June 2007 Contents

EDITORIALLong-Chain Omega-3s from Bone to Brain ............................................................ 2

CARDIOVASCULAR HEALTHEPA Reduces Nonfatal Coronary Events in Statin-Treated Patients

with High Cholesterol ............................................................................................ 3

Supplementary EPA Reduces Atherosclerosis Progression in Type 2 Diabetics .... 5

High Fish Consumption Associated with More Favorable Electrocardiograms ..... 6

EPA and DHA Rapidly Displace Arachidonic Acid in Heart Muscle in Patients with Cardiovascular Disease .................................................................................. 7

Recommendations for Omega-3s in Secondary Prevention of Myocardial Infarction ........................................................................................... 10

MATERNAL AND INFANT HEALTHModest Maternal DHA Supplementation Linked to Improved Infant Visual Acuity ..10

Moderate Maternal Fish Oil Supplementation Increases Cord Blood DHA ......... 11

IMMUNE FUNCTIONEating Fish in Last 4 Weeks of Pregnancy Lowers Chance of Infant Eczema ..... 13

Maternal Fish Consumption in Pregnancy Reduces Chance of Eczema in Childhood ........................................................................................... 14

Fish Oil Supplementation in 9-Month Old Infants Hastens Immune Maturation at 1 Year .............................................................................................15

MENTAL HEALTHLC-PUFAs Improve Behavior in Children with ADHD ......................................... 17

Low n-3 LC-PUFA Status Might Be Linked to Mood and Behavior in Healthy Adults.................................................................................................. 19

Volume of Key Brain Regions Associated with Omega-3 PUFA Consumption .... 20

CLINICAL CONDITIONSAlzheimer’s Disease

Novel Effects of Dietary DHA and Omega-6 DPA on Pathologies in Alzheimer’s Model ................................................................................................ 21

Age-Related Macular DegenerationBoosting DHA & Limiting Arachidonic Acid May Guard Against Advanced AMD ....24

Bone Mineral DensityLong-Chain Omega-3s Linked to Greater Bone Mineral Density in Young Men .... 25

FRONTIERSLipid Rafts in Immune and Cancer Cells ............................................................. 27

PUFA Newsletter • June 2007

PUFA NEWSLETTER STAFF

EditorJoyce A. Nettleton, D.Sc.

Communicat ions ManagerAngela Dansby

SponsorDSM Nutritional Products Kaiseraugst, Switzerland

www.dsm.com

Volume 12 • Issue 2

June 2007 Contents

SCIENCE ADVISORY BOARD

Stephen E. Cunnane, Ph.D. University of Sherbrooke

Quebec, Canada

Stefan Endres, M.D.University of Munich

Munich, Germany

William S. Harris, Ph.D. South Dakota Health Research

Foundation, Sioux Falls, SD

Gerard Hornstra, Ph.D. (retired)

Maastricht University Maastricht, The Netherlands

Maria Makrides, Ph.D. Child Health Research Institute

Adelaide, Australia

Letters and editorial comments should be submitted to Nettleton

at [email protected] and technical comments to Dansby

at [email protected]. Subscribe to the

PUFA Newsletter at www.fatsoflife.com

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This packed issue of the PUFA Newsletter reflects the rapid advances around the world in under-standing polyunsaturated fatty acids (PUFAs).

From enhanced benefits in preventing secondary heart attacks to lower risk of eczema and attention deficit hyperactivity disorder in childhood through increased bone mineral density in late adolescence and slower progression of macular degeneration, the omega-3 PUFAs from fish are revealing their potential to improve health at all ages.

The omega-3 PUFA eicosapentaenoic acid (EPA) reduced the likelihood of major coronary events by 19% and unstable angina by 24% in patients with cor-onary artery disease taking statin medications. It was also associated with less clogged carotid arteries in patients with type 2 diabetes after 2 years. Australian researchers reported direct evidence that EPA and doc-osahexaenoic acid (DHA), another long-chain omega-3 PUFA found almost exclusively in fish, were rapidly incorporated into the hearts of patients with narrowed coronary arteries. This observation suggests that pre-treating coronary patients with fish oil before surgery might lower their risk of major coronary events imme-diately following surgery, when the chance of major coronary events is greatest. The abundant literature on the cardioprotective effects of long-chain omega-3 PUFAs convinced the National Institute for Health and Clinical Excellence in the U.K. to recommend that patients surviving a heart attack consume 1 g/day of long-chain omega-3 fatty acids from oily fish.

Studies among pregnant women and their infants extend the evidence that the consumption of marine omega-3 PUFAs during pregnancy is linked to a lower chance of childhood eczema. Maternal consumption of less than a gram of these PUFAs also increased the level reaching the infant and prevented the usual drop in the mother’s blood levels that occurs late in pregnancy. Findings from another study of pregnant women suggest that fish oil supplementation might hasten the maturation of the infant’s immune system, possibly increasing the infant’s protection against allergic conditions.

In school-aged children with attention deficit hyperactivity disorder, consuming less than a gram of marine PUFAs for 15 weeks led to sig-nificant improvements in inattention, hyperactiv-ity and impulsivity com-pared with children tak-ing a placebo. Continued supplementation for another 15 weeks led to further improvements in these behaviors. This trial is the largest to date examining the effects of marine omega-3s on attention deficit hyperactivity disorder in children.

Two reports focused on diseases of aging–declining bone health and age-related macular degeneration (AMD)–reported positive outcomes associated with higher DHA status. Animal studies have suggested that long-chain omega-3 PUFAs might improve bone mineral density. In this report of young men in their late teens, higher serum phospholipid DHA concen-trations were linked to greater total and spine bone mineral density. Intervention studies with omega-3 PUFAs in postmenopausal women and older men, whose declining bone health increases the risk of fracture, would be most welcome.

Finally, in a recent report from the longitudinal study on nutrient intake and AMD, patients with the condi-tion who ate more than 2 servings of fish/week cut their chances of developing the most advanced stage of the disease by 40%.

From bone to brain, fetus to pensioner and heart to mind, the advantages associated with long-chain omega-3 PUFAs continue to accumulate. Ensuring adequate intake throughout life continues to appear an effective personal health policy.

■ EDITORIAL

Joyce A. NettletonEditor, PUFA and Fats of Life [email protected]

Long-Chain Omega-3s from Bone to Brain

■ CARDIOVASCULAR HEALTH

EPA Reduces Nonfatal Coronary Events in Statin-Treated Patients with High Cholesterol Fish oils and the long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFAs) they contain are associated with significantly lower sudden death and cardiac mortality from coronary heart disease, especially in patients who have survived a myocardial infarction (heart attack). Whether the consumption of fish or n-3 LC-PUFAs can prevent heart disease, per se, is less clear, but evidence from populations consuming fish frequently, such as in Japan, suggest it might. Japan has half the heart disease mortality as in the U.S. and a significantly lower incidence of the disease.

Although the American Heart Association, British Heart Foundation, World Health Organization and other health groups urge people to increase their consumption of fatty fish for cardiovascular ben-efits, preventive medical care includes the prescrip-tion of statin drugs to

reduce low-density lipoprotein (LDL) levels in patients at risk of myocardial infarction. However, statins do not reduce triglyceride levels, which may be elevated in patients with abnormal lipid profiles and independently increase the risk of heart disease. Some evidence sug-gests that patients with combined hyperlipidemia, who consume both n-3 LC-PUFAs and statins have greater protection against endovascular thrombosis than with either treatment alone. Combined therapy is also asso-ciated with reductions in plasma triglycerides and pos-sibly protection against decreased beta-carotene and ubiquinol-10 (a lipid-soluble antioxidant) observed with statins alone. A review published in 2006 concluded that n-3 LC-PUFAs provide additional lipid improve-ments without increased risk of adverse effects on muscle or liver.

Statin therapy with and without n-3 LC-PUFAs has not been evaluated exclusively in patients with hypercho-lesterolemia or for longer than one year. Accordingly, clinical investigators at several universities and hospitals in Japan collaborated to assess the effect of eicosapen-taenoic acid (EPA), an n-3 LC-PUFA, in 18,645 patients with total cholesterol levels of 6.5 mmol/L (250 mg/dL) or higher and an LDL level of 4.4 mmol/L (170 mg/dL) or more. Patients were excluded if they had an acute myo-cardial infarction in the past 6 months, unstable angina

or serious heart disease, such as severe arrhythmia, val-vular disease or congenital heart disease. Other grounds for exclusion were serious conditions, such as malignant disease, uncontrolled diabetes and planned surgery.

Participants in the Japan EPA Lipid Intervention Study (JELIS) included 5,859 men aged 40 to 75 years and 12,786 postmenopausal women aged up to 75 years with or without coronary artery disease. Their average age was 61 years. Participants were divided into two groups according to the presence of coronary artery dis-ease. Those without the condition, numbering 14,981 (80%), comprised the primary prevention group; the remainder constituted the secondary prevention group. Participants were randomly assigned to receive EPA with statin or statin alone. All participants underwent 4 to 8 weeks of washout from hypolipidemic drugs and received dietary advice. Participants and investigators were not blinded to the treatments, although endpoint evaluation was adjudicated by expert cardiologists and a neurologist unaware of patient treatment.

All patients received either 10 mg pravastatin or 5 mg simvistatin once daily for cholesterol-lowering. Patients with uncontrolled hypercholesterolemia (about 10%) received twice the dose of either statin. No other lipid-lowering drugs were permitted. Participants were ran-domized to receive statins + EPA (600 mg as ethyl esters 3 times daily for a total dose of 1,800 mg/day) or statins alone. Blood samples were collected at 6 and 12 months and annually thereafter for the study duration. The average participant time was 4.6 years.

Primary study endpoints were any major coronary event including sudden cardiac death, fatal and non-fatal myocardial infarction and other occurrences, such as unstable angina, angioplasty, stenting or coronary artery bypass surgery.

At baseline, participants had average total and LDL cholesterol values of 7.1 mmol/L (274 mg/dL) and 4.7 mmol/L (181 mg/dL), respectively. Average triglyceride values were in the upper normal range, 1.7 mmol/L (154 mg/dL) and high-density lipoprotein concentrations averaged 1.5 mmol/L (58 mg/dL), levels well within the normal range (>1.0 mmol/L, or 40 mg/dL).

As shown in Figure 1, the group consuming EPA and statins (orange bars) experienced 19% fewer total major coronary events after 5 years compared with those not taking EPA (2.8% vs. 3.5% events, P=0.01). Other non-fatal coronary events taken collectively, such as non-fatal myocardial infarction, angioplasty and stenting, were also 19% less common in the EPA group (240 vs.


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The JELIS Study asked whether EPA could boost the effectiveness of lipid-lowering statin medication in patients with high cholesterol levels and high fish intake.


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297 nonfatal events, P=0.02). In addition, significantly fewer EPA-consuming participants developed unstable angina (147 vs. 193 patients, P=0.01). Treatment groups did not differ in the number of sudden cardiac deaths, fatal myocardial infarctions or coronary deaths.

It is striking that at the end of 5 years, with 15,882 par-ticipants remaining in the study, there were only 586 major coronary events in the entire sample. Even to a casual observer, it is clear that this population is at very low risk of heart disease and coronary mortality. When the outcome data were analyzed according to

the absence or presence of coronary artery disease (pri-mary and secondary prevention groups, respectively), the event reduction rates were similar (18% and 19%, respectively). Since the treatment effect sizes were vir-tually the same in both groups, the failure of EPA to significantly reduce event rates in the primary preven-tion group was more a reflection of inadequate sample size than the magnitude of the effect (Figure 2). In the secondary prevention patients–those with established coronary disease–there was a significant reduction in total major coronary events and in unstable angina in the EPA group compared with the statin-only group (Figure 3). Frequency of all other endpoints did not dif-fer between the treatment groups.

The investigators noted that patients grouped accord-ing to their baseline LDL-cholesterol levels did not differ in their likelihood of having a major coronary event, regardless of treatment. Both treatment groups experienced similar reductions in total and LDL-cho-lesterol concentrations (19 and 25%, respectively), suggesting that EPA exerts its effects via mechanisms

that are independent of a reduction in LDL cholesterol. Triglyceride levels decreased significantly more (9%) in the EPA group than in the statin-only group (4%) (P<0.001), but reductions were greater–about 20%–in patients with elevated triglycerides at baseline. There were minor–but statistically not significant–increases in HDL-cholesterol levels in each group. Overall, the minor effects of EPA on serum lipid patterns were unable to explain the clinical benefits observed.

More patients consuming EPA experienced adverse effects compared with control participants (25% vs. 22%,


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respectively, P<0.0001) and were more likely to discon-tinue participation (12% vs. 7%). Most effects were mild and included increased liver enzymes and blood sugar, gastrointestinal disturbances, skin abnormalities and hemorrhage.

In summary, the JELIS study reported a significantly lower incidence of major coronary events (19%) and a 24% reduced chance of unstable angina in patients with confirmed coronary artery disease and elevated cholesterol levels who consumed EPA with their statin medication. However, the reduction in major coronary events in patients without coronary artery disease, although not statistically significant, was of the same magnitude as that seen in the secondary prevention group. Reduction in major coronary events was unre-lated to LDL-cholesterol levels.

Unlike some other secondary prevention trials, EPA treatment had the greatest effect on non-fatal events, such as unstable angina. In contrast with the findings from the GISSI-Prevenzione study, EPA plus statins did not reduce the likelihood of sudden cardiac or coronary death in these patients with coronary artery disease. A similar observation was reported previously by Iso in a large prospective cohort study in Japan. The JELIS study investigators suggested that people with a high consumption of fish are already protected against sud-den cardiac death and coronary artery disease mortal-ity, and in such patients, supplementary EPA or n-3 LC-PUFAs mainly lowers the risk of nonfatal events. Both the JELIS and Iso studies support the interpretation that high fish consumption reduces the onset and develop-ment of coronary heart disease.

The JELIS study has weaknesses, including possible bias among participants because of the lack of a placebo control, which would be ethically difficult to perform. The high proportion of female participants (about 70%) also reduces the likelihood of coronary events, but demonstrates that EPA has clinically relevant effects on coronary events in women. A population with high fish consumption and nearly 10 times the plasma EPA concentrations as in the U.S. already enjoys substantial protection against heart disease and cardiac mortal-ity. Nevertheless, additional dietary EPA was associated with further reductions in the incidence of nonfatal coronary events. Yokoyama M, Origasa H, Matsuzaki M, Matsuzawa Y, Saito Y, Ishikawa Y, Oikawa S, Sasaki J, Hishida H, Itakura H, et al. Effects of eicosapentaenoic acid on major coro-nary events in hypercholesterolaemic patients (JELIS): a randomized open-label, blinded endpoint analysis. Lancet 2007;369;1090-1098.

Supplementary EPA Reduces Atherosclerosis Progression in Type 2 DiabeticsMajor cardiovascular problems are responsible for about 80% of the mortality in people with diabetes mellitus (diabetes). Impaired circulation in the large and small blood vessels is a frequent diabetic complication. In the larger arteries, lipid deposits, blood clots and plaque impede blood flow, leading to cerebrovascular, periph-

eral artery and cardiovascular dis-eases. This pathol-ogy is known as macroangiopathy. Impaired circula-tion in the small blood vessels, microangiopathy, leads to kidney failure and dia-betic retinopathy. Several causes of damaged blood vessels are specific

to diabetes: for example, the formation of advanced glycation end-products and the desulfation of glycos-aminoglycan. Other vascular problems include reduced nitric oxide production, increased oxidative stress, and endothelial inflammation. Because the consequences of these vascular complications are potentially fatal, there is considerable clinical emphasis on reducing these macro- and microangiopathies. It is believed that careful attention to controlling blood sugar and glycosylated hemoglobin is effective in counteracting diabetic microvascular damage. A more comprehensive approach to improving lifestyle, lipid profile and hyper-tension is required to reduce cardiovascular risks.

To control arterial disease and reduce the chance of thrombosis in diabetic patients, physicians often pre-scribe aspirin, which carries a risk of hemorrhage, gas-trointestinal effects and lack of patient response. An additional therapeutic choice would be n-3 LC-PUFAs. These fatty acids suppress thromboxane production that promotes platelet aggregation and inflammatory responses. They could potentially improve blood flow and the angiopathies associated with diabetes. To find out if n-3 LC-PUFAs affected the progress of macroangi-opathy, investigators at the Juntendo University School of Medicine in Tokyo conducted an open-label prospec-tive trial in 81 diabetic Japanese patients and monitored the progression of atherosclerosis in the carotid artery.

Patients with type 2 diabetes, who did not have serious complications, such as renal, hepatic or overt cardiovas-cular disease, were recruited from the outpatient clinic.

Impaired circulation in large and small blood vessels is a frequent diabetic complica-tion, weakening the walls of the small blood vessels and slowing blood flow. Long-chain omega-3 PUFAs may be a safer alternative to aspirin in improv-ing blood flow and controlling potential thrombosis and atherosclerosis progression.


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Their average age was 60. Patients were randomly divided into 2 groups, matched for age and gender after their first screening visit. Both groups received standard therapy and appropriate medications to con-trol blood sugar, blood pressure and lipids. One group received 1.8 g/day of supplementary eicosapentaenoic acid (EPA), an n-3 LC-PUFA, provided as ethyl ester cap-sules. Participants received bilateral ultrasonography of their carotid arteries, with images taken in 3 different longitudinal projections. Scans of the common carotid artery, carotid bulb and internal carotid artery were used to calculate arterial intima-media thickness. These pictures permit measurement of arterial blockage and changes in the obstructions related to study interven-tions. The technique is commonly used to assess the progression of atherosclerosis.

Study participants also received measurements of their brachial ankle pressure and brachial-ankle pulse wave velocity (evaluations of blood flow) as well as clinical assessments of glycosylated hemoglobin, blood lipids and blood pressure. All measurements were performed at baseline and after 2 years, although patients were monitored every 3 months. Sixty patients completed the study. At baseline, the 2 groups were not signifi-cantly different in clinical assessments or carotid intima-media thickness.

After 2 years, the mean carotid intima-media thickness decreased 4.7% in the EPA group, but increased 2.4% in the control group (Figure 1), a difference that was statistically significant (P=0.03). The maximum intima-media thickness diminished by 11.8% in the EPA group

compared with a decrease of 0.9% in the untreated patients P<0.001). Arterial stiffness, as reflected in the 2.3% decreased brachial-ankle pulse wave velocity mea-surements was reduced in patients consuming EPA, but worsened by 5.4% in the untreated patients. The differ-ence in glycosylated hemoglobin between the 2 groups was not statistically significant. Within-group statisti-cal analysis indicated that the changes in intima-media thickness in patients consuming EPA were statistically significant over the 2-year period. No other clinical parameters differed between the 2 groups. Considering the high fish consumption in Japan, more information on baseline and endpoint EPA status would have been useful. Use of a blinded placebo-controlled study design would have strengthened this study.

Nevertheless, these findings show that when EPA consumption increases, favorable changes in occur in diabetics that may retard atherosclerosis. The study also supports the limited number of studies in various patient populations reporting reduced progression of atherosclerotic plaque related to n-3 LC-PUFA intake or status. For example, women with coronary artery disease and the highest concentrations of phospholipid docosahexaenoic acid (DHA) had the least reduction in artery inner diameter compared with women with lower DHA concentrations. Progression of atheroscle-rotic lesions was slowed in monkeys consuming EPA and in postmenopausal diabetic women consuming 2 or more fish meals/week. These encouraging reports sug-gest that controlled trials of n-3 LC-PUFA supplementa-tion in type 2 diabetic patients are much needed.

Mita T, Watada H, Ogihara T, Nomiyama T, Ogawa O, Kinoshita J, Shimizu T, Hirose T, Tanaka Y, Kawamori R. Eicosapentaenoic acid reduces the progression of carotid intima-media thickness in patients with type 2 diabetes,” Atherosclerosis 2007;191:162-167.

High Fish Consumption Associated with More Favorable Electrocardiograms One way that long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFAs) reduce the chance of sudden car-diac death, the cause of nearly half of all cardiac deaths, is to reduce abnormal heart rhythms. Evidence to sup-port this mechanism of action comes from animal stud-ies, secondary prevention of sudden death in patients with coronary heart disease, modulation of ion chan-nels in heart cells, and other improvements in the elec-trical properties of the heart, such as lower heart rate. However, not all studies have reported favorable out-comes on heart rhythms, particularly in patients with implanted cardioverter defibrillators.

Other reports have described favorable effects of


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n-3 LC-PUFAs on the electrical properties of the heart, such as lower heart rate and higher heart rate variability, but some studies have reported no effects in patients with myocardial infarc-tion or in healthy middle-aged volun-

teers. Additional evidence that fish consumption is asso-ciated with improved electrical parameters in the heart comes from an observational study in Attica, Greece. From a random sample of inhabitants in the Athens area, modified to exclude participants with a history of cardiovascular or atherosclerotic disease or chronic infection, investigators at the University of Athens enrolled 3,042 participants, whose average age was 50 years. Participants’ diets were assessed using a validated food frequency questionnaire. Upon enrollment, partic-ipants underwent assessment of blood pressure, blood lipids, medical history, electrocardiogram, and lifestyle.

Fish intake was divided into 4 categories: none or very rare; rare (<150 g or about 5 oz/week); moder-ate, 150-300 g/week; and frequent, >300 g or nearly 11 oz/week. From the electrocardiographic measure-ments, the QT interval–the time for repolarization of the ventricular myocardium–was determined and cor-rected for heart rate. The mean corrected QT interval, QTc, was calculated in each subject as the sum of the QTc intervals from all measured leads divided by the number of measured intervals.

In this population, fish consumption was associated with age and obesity, but inversely with years of school and hypertension. About 90% of participants reported eating fish at least once/week, mainly sardines, goat-fish, giltheads and tope. Fish consumption was also inversely related to serum triglyceride levels and systolic blood pressure.

Corrected QT interval was inversely and significantly related to fish consumption in both men and women (Figure 1). Men who consumed >300 g fish/week had, on average, a 14% shorter QTc compared with men who did not eat fish. For women, the difference was 13%. When the relationship between fish consumption and QTc inter-val was adjusted for several potential confounders (e.g., nut intake, age, sex, BMI, education, smoking, physical activity, hypertension, hypercholesterolemia, diabetes), QTc remained significantly and inversely related to fish intake. It was also inversely related to nut intake.

These findings support the report of shorter QT interval in participants in the National Heart, Lung and Blood Family Heart Study, who were in the highest tertile of alpha-linolenic acid consumption, and in participants with the highest tuna or baked fish intake in a popula-tion-based cohort in the U.S. They do not concur with findings in post-myocardial infarction patients or in healthy Dutch men and women supplemented with n-3 LC-PUFAs. In the latter study, the consumption of 1.5 g/day n-3 LC-PUFAs for 12 weeks did not affect any char-acteristics of the electrocardiogram in the participants. Thus, inconsistencies among reports and differences in study participants and design limit firm conclusions about the effect of n-3 LC-PUFAs or fish consumption on heart rhythms. It is hoped that a large, randomized, double-blind controlled trial of purified n-3 LC-PUFAs in patients following an acute myocardial infarction, currently underway, will provide more insights into these inconsistencies. In spite of uncertainties about n-3 LC-PUFAs and arrhythmias, the majority of studies in patients with coronary heart disease or at risk of it continue to support significant cardiovascular benefits associated with fish or n-3 LC-PUFA consumption.

Chrysohoou C, Panagiotakos DB, Pitsavos C, Skoumas J, Krinos X, Chloptsios Y, Nikolaou V, Stefanadis, C. Long-term fish consumption is associated with pro-tection against arrhythmia in healthy persons in a Mediterranean region–the ATTICA study. Am J Clin Nutr 2007;85:1385-1391.

EPA and DHA Rapidly Displace Arachidonic Acid in Heart Muscle in Patients with Cardiovascular DiseaseThe fondness of the heart for long-chain omega-3 poly-unsaturated fatty acids (n-3 LC-PUFAs) has been known

Consumption of fish or long-chain omega-3 polyunsatu-rated fatty acids reduces the chance of sudden cardiac death, in part by stabilizing abnormal heart rhythms. However, arrhythmias may not be improved in patients with implanted defibrillators.


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at least since the 1970s, when it was demon-strated that in rats fed cod liver oil the myo-cardium concentrated docosahexaenoic acid (DHA) in its phospho-lipids at the expense of the omega-6 fatty acids, linoleic and ara-chidonic acids. It has

been suggested that one way by which fish oil exerts its cardioprotective effects is by displacing arachidonic acid in heart muscle with eicosapentaenoic acid (EPA) and DHA. Such displacement would reduce the amount of arachidonic acid available for pro-inflammatory, pro-thrombotic mediators such as cytokines and thrombox-anes. Further, increased concentration of EPA and DHA would enhance the production of eicosanoids and anti-inflammatory mediators that counteract the effects of arachidonic acid-derived substances. Such a change would also alter the composition of membrane lipid rafts, which could have a profound effect on cellular signaling pathways (see Frontiers).

The incorporation of n-3 LC-PUFAs into the myocardium has been described in rats, chicks and other experimen-tal animals, but few reports describe the n-3 LC-PUFA concentration in the human heart. In a study in heart transplant patients, the consumption of 1 g/day n-3 LC-PUFAs for 6 months led to a 110% increase in the EPA and DHA concentration in interventricular muscle tissue. Other studies in cardiac patients have reported reduced susceptibility in patients with implanted cardio-verter defibrillators who were infused with n-3 PUFAs and reduced incidence of post-operative atrial fibrilla-tion in coronary artery bypass graft surgical patients, which imply uptake of n-3 PUFAs into the myocardium. Neither report described tissue composition, however.

Two recent reports address this knowledge gap. In a detailed study of the uptake of n-3 PUFAs from fish, flax and olive oils, Robert Metcalf and colleagues at the Cardiovascular Research Center, Royal Adelaide Hospital and the University of Adelaide, Australia, recruited 60 patients undergoing heart surgery for tissue sam-ple donations. Surgical procedures included coronary artery bypass graft and valve repair or replacement. Participants consumed fish no more than once a week and did not take fish oil supplements.

Prior to surgery, patients were randomized to one of 6 treatments: 10 ml/day fish oil concentrate (6 g/day EPA+DHA in nearly equal amounts) for 7, 14 or 21 days, or 10 ml/day of flax (6 g/day alpha-linolenic acid,

ALA) or olive oil for 21 days. One group received no dietary supplement. Participants who failed to consume the supplement or from whom no atrial tissue was obtained were replaced by the next available patient

to ensure 30 speci-mens from patients consuming fish oil and 10 from each of the other groups. Surgery rescheduling resulted in a range of treatment times from 7n to 188 days. Fatty acid composi-

tion was also examined in patients’ red blood cell and plasma phospholipids. The average age of participants was 64 years.

Baseline fatty acid composition of red blood cell and atrial tissue did not differ among treatment groups. Uptake of EPA and DHA into atrial tissue followed a curvilinear pattern with maximum incorporation of DHA achieved in about 20 days and EPA in about 30 days (Figure 1). Although baseline DHA concentration was nearly 10-fold

Little is known about the uptake of long-chain omega-3 polyunsaturated fatty acids in the human heart, but they are believed to exert anti-arrhythmic, anti-thrombotic and anti-inflammatory effects.

Within 2 weeks of consuming 6 g EPA and DHA daily, these fatty acids increased in heart muscle phospholipids by 86%. DHA concentration was nearly 3-fold higher than EPA after 33 days.

Figure 1. Increases in atrial and erythrocyte phospho-lipid EPA and DHA with the consumption of 3 g/day EPA or DHA for up to 63 days. Reproduced from Am J Clin Nutr 2007;85:1222-1228, with permission from the American Society for Nutrition.


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higher than EPA, after 7 days, DHA represented 6.5% and EPA 1.4% of total atrium fatty acids. DHA concentration remained more than twice that of EPA over the course of more than 60 days of fish oil consumption, even though EPA and DHA were provided in equal amounts. At a median of 33 days of fish oil consumption, the level of DHA in atrial tissue was 8.5 ± 1.1% total fatty acids com-pared with 3.0 ± 0.4% for EPA.

EPA and DHA uptake occurred at the expense of ara-chidonic acid, with the pattern of EPA and DHA uptake matching arachidonic acid diminution (Figure 2). ALA did not accumulate in atrium.

Patients consuming flax oil achieved an atrial ALA concen-tration after 29 days of 0.3% total fatty acids compared with 0.1% at baseline. EPA concentration in the flax oil group reached 0.75% compared with the control value of 0.5%, but was only one-quarter the level reached in the fish oil groups (3.0%). DHA concentrations did not differ from the controls. These data indicate that ALA consumed for 29 days in amounts equivalent to EPA and DHA was a poor source of EPA for atrial muscle and had no effect on DHA and arachidonic acid levels.

In contrast to atrial tissue, red blood cells incorporated DHA in a nearly linear fashion with no plateau reached at the end of 60 days. EPA was incorporated in a curvi-linear manner reaching a plateau at approximately 25 days. For the combination of EPA and DHA, the curvi-linear uptake in red blood cells more closely paralleled the uptake pattern in atrial tissue. Uptake appeared to plateau at the end of the study, after about 60 days, whereas in the atrium, combined EPA and DHA reached a plateau after about 40 days. Thus, red blood cell EPA closely follows the pattern in atrial tissue, but for DHA, which is twice as concentrated as EPA in the atrium, red blood cell DHA was a poor predictor of uptake, particu-larly in the first 20 to 30 days. These observations, along with variation in red blood cell n-3 LC-PUFA incorpora-tion from other sources, suggest caution in extrapola-tions to heart tissue from red blood cell fatty acid com-position. The fractional increase in red blood cell n-3 LC-PUFAs may underestimate the increase in myocardial tissue, at least until a new steady state is established.

In another Australian study, 17 patients aged 61 years who were scheduled for coronary artery bypass graft surgery were randomized to consume 4.4 g/day n-3 LC-PUFAs or an olive oil placebo for 6 weeks prior to surgery. Dr. Manohar Garg and colleagues at the University of Newcastle, Callaghan, Australia, reported the fatty acid composition of atrial biopsy tissue obtained at surgery and of plasma obtained at baseline and immediately prior to surgery. Pre-operative plasma n-3 LC-PUFA values confirmed con-sumption of the fish oil capsules. In plasma total lipids, EPA content increased 6-fold, while DHA increased by 3 times. Absolute changes in atrial phospholipid EPA and DHA in the fish oil group compared with the placebo group were 2.3 and 1.7%, respectively. However, concentration of DHA in atrial phospholipids was 3 times higher than EPA, as reported by Metcalf and colleagues. Concentrations of EPA and DHA in atrial phospholipids in the two studies were similar for the 6-week and 33 day values. Incorporation of n-3 LC-PUFAs in the Garg study patients also occurred at the expense of arachidonic acid. Interestingly, in the Garg study, atrial fibrillation occurred in 2 of 9 and 2 of 8 pla-cebo and fish oil patients, respectively.

These findings have several implications for the manage-ment of patients immediately after myocardial infarction and for those with heart disease. Consumption of large amounts of n-3 LC-PUFAs (4 to 6 g/day) leads to the rapid incorporation of EPA and DHA in the atrium in the first month, the period when survivors of a myocardial infarc-tion are at the greatest risk of sudden death. Within 1 week of fish oil consumption, EPA plus DHA increased by 54%, reflecting their rapid uptake into the atrium. DHA concentrations in the atrium are about 3 times those of EPA. The concurrent reduction in atrial arachidonic acid

Figure 2. Exchange of atrial phospholipid EPA and DHA with arachidonic acid as a function of duration of treatment. Reproduced from Am J Clin Nutr 2007;85:1222-1228, with permission from the American Society for Nutrition.


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with the consumption of fish oil may lower the chance of unstable arrhythmias, inflammatory responses and thrombus formation. Flax seed oil was only about 10% as effective as fish oil in raising atrial EPA plus DHA or EPA concentrations. It had no effect on atrial DHA levels and did not itself accumulate in heart muscle. The clini-cal implication for heart patients facing cardiac surgery is that the consumption of fish oil prior to surgery can ensure abundant n-3 LC-PUFAs in the heart that may diminish the amount and metabolic consequences of unopposed arachidonic acid.

Metcalf RG, James MJ, Gibson RA, Edwards JR, Stubberfield J, Stuklis R, Roberts-Thomson K, Young GD, Cleland LG. Effects of fish-oil supplementation on myocardial fatty acids in humans. Am J Clin Nutr 2007;85:1222-1228.

Garg ML, Leitch J, BlakeRJ, Garg, R. Long-chain n-3 polyun-saturated fatty acid incorporation into human atrium fol-lowing fish oil supplementation. Lipids 2006;41:1127-1132.

Recommendations for Omega-3s in Secondary Prevention of Myocardial InfarctionThe National Institute for Health and Clinical Excellence (NICE), an independent organization in the U.K. that works with the country’s National Health Service, announced its revised guidelines for the secondary prevention of myo-cardial infarction (MI), in May 2007.

For lifestyle changes for after a myocardial infarction, the NICE guidelines say: • Patients should be advised to consume at least 7 g of omega-3 fatty acids/ week from 2 to 4 portions of oily fish; • For patients who have had an MI within 3 months and who are not achieving 7 g of omega-3 fatty acids/week, consider providing at least 1 g daily of omega-3-acid ethyl esters treatment licensed for secondary prevention post MI for up to 4 years; • Initiation of omega-3-acid ethyl esters supplements is not routinely recommended for patients who have had an MI more than 3 months earlier; • Patients should be advised to eat a Mediterranean- style diet (more bread, fruit, vegetables and fish; less meat; and replace butter and cheese with products based on vegetable and plant oils).

■ MATERNAL & INFANT HEALTH

Modest Maternal DHA Supplementation Linked to Improved Infant Visual AcuityInfant visual development is related to the availability of docosahexaenoic acid (DHA), a long-chain omega-3

polyunsaturated fatty acid (n-3 LC-PUFA) found mainly in fish and fish oils, but present also in human milk and DHA-supplemented infant formula. The importance of DHA in retinal function is reflected in the high concen-tration of DHA in retinal photoreceptor outer segments, where it is involved in the intercellular signaling pathway that transforms light signals to neuronal activity.

The developing fetus concentrates LC-PUFAs from the maternal circulation during the last tri-mester of pregnancy. Several studies have shown that term infants with higher intakes of DHA or higher red blood cell DHA have improved

visual acuity, a sensitive measure of visual function in the first few months of life compared with infants with low DHA intakes or status. However, not all studies have confirmed this observation in term infants.

Different assessment techniques for visual acuity may affect the variation in reported outcomes. Techniques such as the electroretinogram and visual evoked potential assess the function of the whole retina and responsive-ness of the visual cortex, respectively, whereas behavioral measures of acuity provide the most direct measure of what an infant actually perceives. Evidence suggests that maternal supplementation with n-3 LC-PUFAs increases maternal and infant DHA status, although not all stud-ies have reported increased DHA levels in cord blood. Similarly, the literature is inconsistent on the effects of maternal n-3 LC-PUFA supplementation during pregnancy and infant visual acuity. Studies measuring visual evoked potentials and electroretinograms in healthy term infants suggested that DHA supplementation during pregnancy had no effect on infant visual acuity.

To address this question, Michelle Judge and colleagues at the University of Connecticut, Storrs, USA, recruited 30 pregnant women 18 to 35 years of age who had less than 20 weeks gestation. Women were randomly assigned to consume cereal bars containing 300 mg DHA or corn oil that were otherwise identical. Women in each group consumed 3, 5 or 7 bars weekly from 24 weeks of pregnancy to delivery. The bars provided 130 to 300 mg DHA/day, whereas the background diet for both groups provided about 80 mg DHA/day.

Infants were assessed for visual acuity using the Teller Acuity Cards when they were 4 and 6 months old. At

Term infants with higher intakes of DHA have improved visual acuity in early life in several, but not all, studies. There are no data on behavioral measures of visual acuity related to maternal DHA consumption in pregnancy.


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birth, infants of mothers who consumed the DHA bars were more likely to be female, have a higher APGAR score and have mothers who gained more weight during pregnancy. Mean birthweight did not differ between the 2 groups. Infants were fed breast milk or formula with or without DHA or a combination of breast feed-ing and formula without DHA. Methods of feeding the infants did not differ between the 2 groups.

At 4 months of age, infants whose mothers consumed the DHA bars had significantly higher mean visual acuity scores compared with the placebo infants (Figure). By 6 months, acuity scores in both groups had increased, but no longer differed significantly from each other . These observations were independent of what the infants consumed after birth. Behavioral visual acuity typically develops rapidly in the first 6 months, then slows for the next 6 months, approach-ing adult values at approximately 3 to 5 years of age. Thus, it is not surprising that differences might not persist at later times, as visual acuity continued to improve in both groups. Given that the background diet of these mothers pro-vided typical, but little, DHA, 80 mg/day compared with recommendations in the 200 to 300 mg/day range, unsupplemented mothers may have had sub-optimal n-3 LC-PUFA status during pregnancy that may have limited DHA availability to their infant’s reti-nas. This study supports the importance of adequate maternal DHA consumption during pregnancy. It sug-gests that modest increases in daily DHA, about 200 mg, provided in consumer-friendly foods may make a measurable difference to an infant and are acceptable to mothers.

Judge MP, Harel O, Lammi-Keefe CJ. A docosahexaenoic acid-functional food during pregnancy benefits infant visual acuity at four but not six months of age. Lipids 2007;42:117-122.

Moderate Maternal Fish Oil Supplementation Increases Cord Blood DHA

Estimates of fish intake, and hence the consumption of long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFAs) varies substantially among countries. Except for some island countries and coastal areas, such as Japan, western countries consume relatively modest amounts of fish. Many women of child-bearing age have low fish intakes that may provide suboptimal amounts of doco-sahexaenoic acid (DHA) for fetal neurodevelopment. Several studies have reported improved outcomes in infants whose mothers consumed supplemental DHA during the later stages of pregnancy.

Pregnancy increases the need for many nutrients besides n-3 LC-PUFAs, such as iron, folic acid and pro-tein, although recognition of the importance of n-3 LC-PUFAs for infant development and maternal well-being has been relatively recent.

A 3-country random-ized double-blind trial was undertaken in Germany, Spain and Hungary to compare the effects on pregnancy out-comes of providing supplementary folic

acid and n-3 LC-PUFAs during pregnancy to healthy women aged 18 to 41 years. Women between 12 and 20 weeks’ gestation, who were free of chronic diseases and not taking fish oil supplements, were recruited from university-linked obstetric centers in each country. Participants were randomized to one of 4 groups: fish oil providing 500 mg DHA and 150 mg EPA/day, 400 µg folic acid (5-methyltetrahydrofolate) acid/day, fish oil plus folic acid, or a placebo, with all groups receiving identical vita-min and mineral supplements without folic acid.

A total of 311 women enrolled in the study and 270 com-pleted it. Blood samples were obtained from 243 mothers and cord blood from 200 infants. After randomization to treatment groups, there were no significant differences in the baseline characteristics among the groups.

Primary outcomes were DHA and EPA in plasma phos-pholipids at 30 weeks’ gestation and delivery and DHA in cord blood plasma phospholipids. Other maternal health

In a 3-country study of healthy pregnancies, mothers were supplemented with fish oil, folic acid, both supplements or a placebo from the 20th week of gestation until delivery.


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parameters included weight gain, delivery complications and postnatal depression. Additional infant measures recorded were Apgar score, birthweight and length.

At the end of the supplementation period, there were no significant differences among the groups in length of gestation, maternal or fetal complications, birth out-comes or maternal postpartum depression.

In maternal plasma phospholipids and cord blood, fish oil was associated with a significant increase in DHA concentration. EPA levels also increased in these mothers until delivery, in spite of the relatively small amount of EPA provided. According to a 3-way analysis

of variance, addition of folic acid to the fish oil supple-ment had a small but enhancing effect on maternal plasma phospholipid DHA compared with fish oil alone (Figure 1). This effect was not observed in cord blood DHA (Figure 2). Folic acid alone did not affect mater-nal DHA concentrations.

DHA and folic acid interaction was previously reported in this study, with significantly higher maternal folic acid levels observed in the fish oil plus folic acid group compared with the folic acid only mothers. The com-bined supplement was also associated with increased placental cell proliferation. In this study, folic acid had a modest effect on increasing plasma phospholipid DHA levels in maternal, but not cord blood.

In the scientific literature, fish oil supplementation significantly increased cord blood DHA concentrations when it 3.7 or 2.7 g/day n-3 LC-PUFAs, but not when provided at 200 mg DHA/day or 135 mg/day. In the present report, 650 mg/day n-3 LC-PUFAs, of which 500 mg was DHA, was sufficient to raise cord DHA levels significantly. The authors commented that dose, dura-tion of supplementation and maternal DHA status may affect transfer of DHA to the fetus. Mothers whose DHA stores are low may preferentially transfer dietary DHA to the fetus, whereas mothers with adequate stores have no need to increase fetal transfer.

The implications of these observations in the context of previous reports suggest that pregnant women

with habitually low fish consumption might benefit from generous intakes of n-3 LC-PUFAs during pregnancy. Fish consumption and breast milk DHA levels in many western countries are low, suggesting

that both maternal and infant nutrition might benefit from increased maternal consumption of n-3 LC-PUFAs. Even small increases of n-3 LC-PUFAs, as reported in the preceding report may benefit infant development.

Krauss-Etschmann S, Shadid R, Campoy C, Hoster E, Demmelmair H, Jimenez M, Gil A, Rivero M, Veszpremi B, Decsi T, Koletzko BV for the Nutrition and Health Lifestyle (NUHEAL) Study Group. Effects of fish-oil and folate supplementation of pregnant women on maternal and fetal plasma concentrations of docosahexaenoic acid and eicosapentaenoic acid: A European randomized multi-center trial. Am J Clin Nutr 2007;85:1392-1400.

Dose and duration of fish oil supplementation in pregnancy as well as maternal DHA status may affect DHA transfer to the fetus. Mothers with low DHA stores may preferentially transfer DHA to the fetus.


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■ IMMUNE FUNCTION

Eating Fish in Last 4 Weeks of Pregnancy Lowers Chance of Infant EczemaThe maturation of the immune system begins in utero and continues through the first 2 years of life. The fetus is capable of producing immunoglobulin E (IgE) and already has mature CD4+ and CD8+ T-cells (thymus or T-cells with specific surface proteins involved in T-cell acti-vation), indications of a functioning immune system. Sensitization of the fetal immune system is believed to result from low-level exposure to antigens from food and the environment that cross the placenta. This is one reason why maternal diet during pregnancy is consid-ered a potential modulator of fetal and infant immune

responses, including the development of atopic disease. Other factors, such as fam-ily history of allergic disease, intake of vita-mins D and E, zinc and birth order affect the development of the fetal immune system.

The fetal environment is considered critical to the sub-sequent development of atopic disease. In addition, long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFAs) may reduce the development of atopic dis-ease because of their anti-inflammatory properties. Studies have reported reduced atopy in infants associ-ated with frequent maternal fish consumption during pregnancy and less severe atopic disease, with signifi-cantly fewer positive skin prick tests, in infants whose mothers were supplemented with fish oil in pregnancy. In contrast, higher breast milk n-3 LC-PUFA levels were associated with greater sensitization in infants at 6 and 24 months of age.

Relatively few studies have examined the effect of mater-nal diet on the prenatal development of allergic dis-ease. In this report, researchers at the National Research Center for Environment and Health, Neuherberg, Germany and colleagues at several German universi-ties collaborated to examine the relationships between various foods consumed by mothers in the last 4 weeks of pregnancy and the prevalence of allergies in their infants at 2 years of age.

Infants were recruited from 3,097 healthy newborns enrolled in a cohort study of lifestyle factors and the immune system. Data and blood samples were available for 2,641 children who were free of chronic diseases. Information about the children’s health was obtained

from parent-completed questionnaires obtained every 6 months during the children’s first 2 years of life. Lifetime prevalence of eczema was based on responses about doctor-diagnosed eczema any time during the 2-year follow-up period.

Investigators assessed children’s allergic sensitization to food allergens as a serum IgE concentration ≥0.35 kU/L against pediatric food allergens egg, cow’s milk, wheat,

peanut, soybean and cod. Positive screening IgE values were followed by measurements of the single allergens for egg, cow’s milk and peanut.

Sensitization to inhaled allergens used the same IgE screening test as for food allergens, substi-tuting a mix of house dust, German cockroach, cat dander, mixed molds

or seasonal allergens, such as timothy grass, mugwort and birch pollen.

Lifetime prevalence of doctor-diagnosed eczema and allergic sensitization among 2,518 children was 17.7%. Sensitization to food allergens occurred in 9.3% of chil-dren and to inhalant allergens in 4.5%. Allergic sensiti-zation to food allergens was significantly more preva-lent in children whose mothers had a high intake (≥2-3 times/month) of celery or citrus fruit (3-4 times/week). Significantly more frequent sensitization against inhal-ant allergens occurred in children whose mothers had a high intake of raw sweet peppers (≥2-3 times/month). In logistic regression analysis, adjusted for potential confounders and dietary variables, high fish intake was the only food with a significant protective effect against the likelihood of developing eczema.

These observations suggest that mater-nal diet in the last 4 weeks of pregnancy could affect the devel-opment of allergic dis-eases in the offspring. The most commonly identified foods linked to increased chance of

allergies were celery, citrus fruit, raw sweet peppers, margarine, vegetable oils and deep-frying vegetable fat. Children whose mothers consumed cream 3-4 times/week were more likely to become sensitized to

Maternal diet during pregnancy affects the maturation of the infant’s immune system. Consuming fish during pregnancy may reduce the risk of childhood allergic diseases.

Foods consumed in pregnancy associated with allergic sensitization in children at age 2: • Celery• Citrus fruits• Raw sweet peppers• Margarine• Vegetable oils• Deep-frying vegetable oils

High maternal fish intake during the last 4 weeks of pregnancy was the only food with a significant positive effect against the likelihood of developing eczema in childhood.


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cow’s milk. Fish was the only food with significant pro-tective effects against eczema. This observation accords with other epidemiological studies, most recently in 5-year-old Dutch children, whose mothers consumed fish during pregnancy. Whether fish consumption dur-ing pregnancy directly affects the cause(s) of childhood allergic sensitization remains to be evaluated in ran-domized controlled trials. Given the increasing preva-lence of certain childhood allergic conditions in several parts of the world, it would be useful to identify poten-tially protective factors.

Sausenthaler S, Koletzko S, Schaaf B, Lehmann I, Borte M, Herbarth O, von Berg A, Wichmann H-E, Heinrich J for the LISA Group. Maternal diet during pregnancy in relation to eczema and allergic sensitization in the offspring at 2 y of age. Am J Clin Nutr 2007;85:530-537. Maternal Fish Consumption in Pregnancy Reduces Chance of Eczema in ChildhoodMaternal diet during pregnancy appears to be an important modulator of immune system maturation in the fetus and may affect the chance of infant atopy. The hope is to identify foods that affect the development of allergic diseases in the infant, especially those with a family history of allergies. Several foods have been identified as being protective or reducing risk of atopy and others that increase its likelihood. Sometimes there is overlap between the two groups. For example, citrus fruit and fruit juices have been reported to increase risk in some studies and to protect against it in others.

Low intake of long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFAs) in the presence of high consumption of n-6 PUFAs, mainly linoleic acid, has been suggested as a maternal factor increasing the risk

of infant atopy, in part because of the pro-inflammatory effects of n-6 PUFAs. Some reports suggest that reducing the consumption of n-6 PUFAs and increasing the intake of n-3 LC-PUFAs in early childhood may be ineffective or actually increase the risk of atopy in high-risk infants. A large epidemiological study suggested that early intro-duction of fish into the infant’s diet is associated with lower risk of allergic disease in childhood.

On the other hand, there is evidence that increasing maternal intake of n-3 LC-PUFAs during pregnancy may

lower the likelihood of infant atopy. For example, infants of atopic mothers who consumed fish oil had reduced cytokine responses to allergens and less severe allergic disease compared with infants of mothers consuming the placebo. In a study from Germany, infants whose moth-ers consumed fish 1 to 2 times/week had a significantly lower chance of developing eczema than infants whose mothers ate fish less often. In Mexico, infants whose mothers ate fish 2.5 times/week were 37% less likely to develop eczema and 35% less likely to have a positive skin-prick test at 6 years of age compared with children whose mothers ate fish only once/week.

In this study, Dr. Saskia Willers and colleagues at the University of Utrecht, the Netherlands, and the University of Aberdeen, Scotland, examined the rela-tionship between the foods consumed during preg-nancy and the development of allergies in the off-spring at age 5. The investigators recruited healthy pregnant women of median 12 weeks of gestational age for dietary assessment and evaluation of atopic status by skin-prick testing. Participants were contacted 5 years after childbirth for assessment of food intake and the 5-year-old child’s health outcomes and diet. Parents reported the child’s food intake over the previ-ous 3 months using a semi-quantitative questionnaire. Children’s health outcomes were assessed by parental questionnaire addressing the child’s history of wheez-ing, asthma, eczema and hay fever, doctor confirma-tion of the condition(s) and past and current treatment for the condition(s). Other assessments of the children included spirometry, use of a bronchodilator, skin-prick test and exhaled nitric oxide.

From 2,000 pregnant women, there were 1,924 mothers with live births and 1,751 food frequency questionnaires. Children’s symptom questionnaire data were available from 1,253 mothers and maternal food intake data from 1,212 of those. Mothers responding to the food intake questionnaire had significantly different food intakes for some food groups compared with non-responding mothers, but the differences were less than 10%.

The most prevalent atopic conditions in the 5-year-old children were eczema (doctor-confirmed 30.4%), asthma (doctor-confirmed 11.6%), and hay fever (doc-tor-confirmed 5.4%), with atopic sensitization occurring in 21.3% of the children. Prevalence of the mother’s ever having these conditions was: hay fever, 25%; eczema, 17%; asthma, 15%; and atopic sensitization, 36%.

For most food groups, there were no consistent asso-ciations between maternal intake and atopic outcomes in children. Thus, these observations do not confirm increased risk of atopic disease reported in German

Maternal diet during pregnancy may reduce the chance of childhood allergic disease, but appropriate interventions are uncertain. Some foods may be protective and others increase the chance of atopy. Maternal intake of n-3 LC-PUFAs may be protective.


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children with frequent maternal consumption of celery, citrus fruits, raw sweet peppers, margarine, vegetable oils or deep-frying oils. However, there were two foods with protective effects on the likelihood of atopic con-ditions: apples and fish.

There was a significant inverse association between maternal total fish consumption and the child’s likeli-hood of having doctor-confirmed eczema and currently receiving eczema medication (Figure). The lowest risks were observed with maternal fish consumption of once or more/week. The mother’s intake of oily fish was asso-ciated with lower risk of doctor-confirmed hay fever, but not with current or ever experiencing hay fever. Consumption of 1 or more portions of oily fish/week was significantly associated with reduced likelihood of ever having hay fever (Odds Ratio= 0.28, P=0.04) in multivariate analysis, but there was no linear trend. There were no consistent associations between a child’s consumption of fish, oily fish or apples and respiratory or allergic symptoms at age 5.

Willers’ study adds to the growing evidence that inter-vention through maternal diet in pregnancy may affect the fetus’ immune system and may be an appropriate time to influence the chance of childhood atopic dis-eases. It confirms other studies reporting a beneficial effect of maternal fish consumption on eczema and positive skin-prick test, eczema, asthma and severity of neonatal atopic dermatitis in infants and young chil-dren. No other food consumed during pregnancy other

than apples affected the occurrence of atopic diseases in the offspring. On the other hand, plasma n-3 and n-6 PUFA levels in infants and children were not associated with wheeze, eczema or atopy in the Childhood Asthma Prevention Study in Australia. The avoidance of allergens has been the primary strategy to prevent asthma and atopy; ongoing trials confirm the effectiveness of this approach. More randomized trials with fish consumption or n-3 LC-PUFAs are needed to solidify the direction indi-cated by this and other epidemiological studies.

Willers S, Devereux G, Craig L, McNeill G, Wijga A, Abou El-Magd W, Turner S, Helms P, Seaton A. Maternal food consumption during pregnancy and asthma, respiratory and atopic symptoms in 5-year-old children. Thorax 2007; online Mar 27. doi:10.1136/thx.2006.074187

Fish Oil Supplementation in 9-Month-Old Infants Hastens Immune Maturation at 1 Year Development and maturation of the infant’s immune system has attracted recent attention because of the dif-ferences in maturation between breast- and formula-fed infants. Supplementation with long-chain polyunsatu-rated fatty acids (LC-PUFAs) also enhanced maturation of

infant immune func-tion. At birth, the infant is able to pro-duce an antigen-spe-cific T-cell response and is already sensi-tized to some anti-gens, but its immune system is not fully functional. For exam-

ple, it has limited ability to produce cytokines, media-tors of immune responses, and its T helper (Th) cells are polarized toward the Th2 type typical of the mother. With maturation, Th1 helper cells predominate, as they do in adults. The prevalence of the Th2 cells enables the infant to recognize low levels of antigens and generate a protective immunoglobulin E (IgE) response.

It is thought that certain periods, particularly during pregnancy, nursing and the introduction of formula and solid foods, might be appropriate times to influ-ence immune system development. Such opportunities are of special interest for the prevention or inhibi-tion of allergic responses and atopic diseases. Several investigators have explored whether fish consumption or the provision of fish oil or omega-3 (n-3) LC-PUFAs to mothers in pregnancy might reduce the likelihood of childhood allergies and atopic conditions, such as eczema, rhinitis and asthma. It has been known for some time that children with atopic conditions have altered PUFA levels, including elevated IgE levels.

It is thought that certain periods, particularly during pregnancy, nursing and the introduction of formula and solid foods, might be appropriate times to influence immune system development.


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In one observational study, children of mothers with asthma were less likely to develop asthma if maternal fish consumption in pregnancy was at least monthly.

Findings among children who consumed fish have been inconsistent. In an a large observational study, chil-dren who consumed fish early in life, between 3 and 8 months of age, were less likely to develop atopic dis-eases compared with children who first consumed fish at 9 months of age or older. In the Australian Childhood Asthma Prevention Study, the prevalence of asthma, wheezing, eczema or atopy at 5 years of age was not affected by the consumption of fish oil added to infant formula or first solid foods. A study of maternal fish oil supplementation in pregnancy reported lower neona-tal cytokine responses, reduced likelihood of sensitivity to egg at 1 year of age and less severe atopic disease.

An infant’s immune system becomes functional through exposure to bacte-ria at the time of birth, immunologi-cal factors in breast milk, environmen-tal allergens (pets, dust mites etc.) and

the introduction of solid foods. Although immune system function may be altered by increased consumption of LC-PUFAs, there is limited information about the effects of n-3 LC-PUFAs on immune system maturation in infants. It is known, for example, that infants fed formula supple-mented with LC-PUFAs have immune system responses resembling those of breast-fed infants and that are more mature than in infants fed unsupplemented formula. In this report from Denmark, researchers describe the effects on the infants’ immune systems of 3 months of fish oil supplementation begun at 9 months of age.

Ninety-four healthy term infants were recruited for the study, of which 83 completed it and 64 had available blood samples at 1 year of age. Infants were randomized to consume either 5 mL/day of a fish oil supplement, providing 168 mg eicosapentaenoic acid (EPA) and 112 mg docosahexaenoic acid (DHA)/mL/day or no supple-ment. The study was unmasked as no placebo was used. Average consumption of the supplement was 3.4 mL/day or 952 mg EPA+DHA/day. Infants were further random-ized to consume either standard infant formula or whole cow’s milk. Infants were examined at the beginning and end of the 3-month intervention. Blood samples, infant weight and length, and allergy diagnosis information (confirmed by a doctor) were collected at each visit. There were only slight differences among the groups in

infant length, body mass index and sex distribution.

Blood samples for both 9- and 12-month visits were obtained from 49 of the 64 infants. Cytokine concen-trations were measured in plasma, while cytokine pro-duction was evaluated in whole blood. Fatty acids were determined in red blood cells. Fish oil consumption increased red blood cell n-3 LC-PUFAs at the expense of linoleic and arachidonic acids as expected. It had no effect on plasma C-reactive protein, IgE and soluble interleukin-2 receptor concentrations. Infants consum-ing formula had higher soluble interleukin-2 receptor values compared with the infants fed cow’s milk, but other immune markers did not differ between the milk and formula groups.

In terms of cytokine production, infants consuming fish oil had significantly greater production of inter-feron-gamma at 12 months compared with infants not receiving fish oil. Measurement of cytokine production was stimulated by L. paracasei and responses adjusted for milk group and 9-month values. There was a ten-dency for lower interleukin-10 production in the fish-oil infants that was inversely related to red blood cell EPA content (P=0.02). These observations would be consistent with current thinking about immune system maturation. During maturation, the infant’s Th2-cell polarized immune system gradually shifts to favor Th1 responses. Th1 cells produce interferon-gamma and promote the differentiation of thymus helper cells to

Infants fed formula supple-mented with LC-PUFAs have immune system responses resembling those of breast-fed infants. These responses are more mature than in infants fed unsupplemented formula.

Table 1. Effect of 3-months of fish oil consumption on productionof selected cytokines in whole blood cultures stimulated with L. paracasei in 12-month old infants

Immune parameter* No fish oil Fish oilTNF-alpha, µg/L 9 mo 19.0 ± 2.6 22.3 ± 2.5 12 mo 25.8 ± 1.9 23.0 ± 1.3 12 mo adjusted† 26.6 (21.9-31.3)§ 23.0 (18.6-27.3)INF-gamma, ng/L 9 mo 559 (157-2450)¶ 785 (16-2819) 12 mo 593 (16-3893) ¶ 640 (48-3461) 12 mo adjusted† 447 (281-710)§ 845 (559-1279)IL-10, ng/L 9 mo 114 ± 22 111 ± 23 12 mo 413 ± 71 341 ± 50 12 mo adjusted† 518 (344-693)§ 355 (200-511)

*Mean ± SEM

†Adjusted for milk group and 9-month values

§Mean (95% confidence interval) by ANCOVA

¶Median (range)


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Th1 cells. Increased production of interferon-gamma in the fish oil infants would foster the development of Th1 cells. Interleukin-10 is also thought to drive the differen-tiation of regulatory T-cells and may be a marker of Th2 cells. A decrease in interleukin-10 would be consistent with diminution of Th2 cells in favor of Th1 cells.

The authors commented that, at this high level of fish oil, there was no indication that innate immunity or general inflammatory responses were affected. Thus, it is unlikely that the study infants were any less protected from invasive microorganisms than non-participants. This study supports the evidence that 9-month old infants consuming LC-PUFAs as fish oil have accelerated maturation of their immune system.

Damsgaard CT, Lauritzen L, Kjaer TMR, Holm PMI, Fruekilde M-B, Michaelsen KF, Frokiaer H. Fish oil sup-plementation modulates immune function in healthy infants. J Nutr 2007;137:1031-1036.

■ MENTAL HEALTH

LC-PUFAs Improve Core Behaviors in Children with ADHDOne of the most prevalent cognitive and behavioral problems in childhood is attention deficit/hyperactivity disorder (ADHD). It affects from 3% to 11% of children in Australia, Europe and the United States, predomi-nantly boys. Children with the condition have little control over their impulsive, hyperactive behavior and often experience other learning difficulties and psy-chiatric problems, such as anxiety, mood disorders and antisocial behaviors. Difficulties from childhood ADHD persist into adulthood in more than half of affected children. Current medical treatments are suboptimal with regard to effectiveness and side effects.

Altered polyunsat-urated fatty acid (PUFA) metabolism, particularly involv-ing the long-chain omega-3 PUFAs (n-3 LC-PUFAs) found mainly in fish, has been implicated in ADHD and other closely related

developmental disorders. Findings involving PUFA treat-ments, mostly from small studies, have been inconsistent and highly variable in design, dose and combination treat-ments. Recent studies using fish oil and omega-6 PUFAs

have provided promising results in improved behaviors and reading and spelling scores. However, when multiple treatments are involved with inadequate control groups, it is difficult to interpret the results. In addition, border-line nutritional status or deficiencies in several nutrients complicate findings of PUFA treatments.

Recognizing these difficulties, Drs. Natalie Sinn and Janet Bryan at the University of Adelaide, Australia, conducted a study among ADHD children, separating the effects of PUFAs from vitamin and mineral supple-mentation. Children 7 to 12 years old, with Conners ADHD Index scores ≥2 SD above the general popula-tion average who were not taking medications were recruited from the community and categorized by age and sex, then randomly allocated to 1 of the 3 treat-ments. Interventions were supplementation with PUFAs alone, PUFAs with vitamins and minerals, or a placebo (palm oil). After 15 weeks on the assigned treatment, all participants were given the PUFAs with vitamins and minerals. The PUFA supplement contained fish oil pro-viding 93 mg eicosapentaenoic acid (EPA) and 29 mg docosahexaenoic acid (DHA), and evening primrose oil providing 10 mg gamma-linolenic acid (GLA) per cap-sules. Children were asked to consume 6 capsules/day, providing a total daily supplement of 558 mg EPA, 174 mg DHA and 60 mg GLA.

Of 182 children aged 7 to 12 years who attended their first appointment, 167 had qualifying Conners scores and 132 completed the first 15 weeks of the study. In total, 109 participants completed 30 weeks in the study. Data were available from 104 of the 15-week participants and 87 of the 30-week children. Behavioral assessments included both parent and teacher Conners Rating Scales (revised) and intelligence quotient (IQ) estimated with the Wechsler Intelligence Scale for Children, version 3.

Investigators com-pared the results in both groups consuming PUFAs with the pla-cebo group and observed statisti-cally significant (by analysis of cova-riance) improve-

ments in the Conners Parent Rating Scales in 9 of 14 variables or subscales. Lower scores indicate improve-ments. Except for the hyperactivity subscale, which was significant at the 0.05 probability level, all were signifi-cant at the <0.01 probability level. Using an analysis of variance for treatment x condition interactions, the

Emerging evidence suggests that children with attention deficit/hyperactivity disorder may respond to long-chain polyunsaturated fatty acids, but most studies are too small or involve too many interventions to sort out what is effective.

After 15 weeks of consuming EPA, DHA and GLA, children with ADHD had significant improvements in inattention, hyperactivity, impulsivity and other indices compared with those taking a placebo.


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investigators found no additional improvements in the children consuming both PUFAs and vitamins and min-erals compared with those taking only PUFAs. At the end of 15 weeks, there were significant improvements (P<0.01) in the children consuming PUFAs in: cognitive problems/inattention, ADHD index, restlessness/impul-sivity, total global assessment score, DSM-IV (diagnostic criteria) scores for inattention, hyperactivity/impulsiv-ity, total DSM-IV score and in oppositional behavior (Figure). There was significant improvement in hyper-activity scores at the 5% probability level.

In the second 15-week phase, assessment scores for the children initially consuming the placebo were com-pared at 30 weeks, after 15 weeks of PUFA consump-tion. Similarly, children initially consuming PUFAs were compared at 15 and 30 weeks, to see whether their scores continued to improve. As expected from the results after 15 weeks, once the placebo children had consumed the PUFA supplements, they had significantly improved scores as the first PUFA groups in the same outcome variables and in social problems and perfec-tionism (P<0.01). The crossover group also exhibited sig-nificant improvement (P<0.05) in oppositional, anxious and psychosomatic assessment scores. Emotional lability was the only variable that was unaffected by any treat-ment in any group.

After 30 weeks (Figure), the groups initially consum-ing PUFAs continued to experience significant (P<0.01) improvements in 8 of the 9 assessments that had improved in the first 15 weeks and in perfectionism (P<0.05). Overall, 30% to 40% of the children had improvements greater than 1 SD by 15 weeks, with the

proportion of children showing improvements increas-ing to 40% to 50% by 30 weeks.

None of the teacher rating scales showed significant improvements in the PUFA groups compared with the placebo group, or following 15 weeks of crossover. It is unclear why this was so, as teacher and parent assess-ments are preferred for clinical purposes. Agreement between the two sources of ratings may be less in cer-tain environments and the authors discuss this issue.

This study is note-worthy for several reasons, including its dramatic find-ings. Its strengths include randomized placebo-controlled study design, partic-ipants free of medi-cation, substantial improvements in core ADHD behav-iors and effective-

ness of treatment in about half of the participants. These findings suggest that PUFAs are likely involved in the man-ifestation of ADHD symptoms. It is noted that the core behaviors of ADHD–hyperactivity, impulsivity and inat-tention–improved from the upper clinical range on the Conners index to the mildly clinical range after 30 weeks. It is not known whether these symptoms would continue to improve with longer supplementation. However, for unknown reasons, at least half of the children appeared not to respond to the intervention, indicating that in those who did, the responses were extensive.

The provision of vitamins and minerals at the recom-mended daily doses did not affect any outcomes. However, this study does not eliminate the possibil-ity that higher doses of vitamins and minerals may be needed in these children. The authors noted that not all participants had a formal diagnosis of ADHD and that not all children with behavioral problems have abnormalities in PUFA metabolism. Issues pertinent to the study, such as analysis of only those completing the trial, compliance, lack of nutritional and biochemical data, and others are discussed in the paper and will be of interest to those wishing more details.

This is the largest randomized, placebo-controlled trial published that examines PUFAs and ADHD. Its results sup-port several previous smaller trials with LC-PUFAs. The findings confirm the potential benefits, without adverse side effects, of LC-PUFA supplementation in children with ADHD for whom safe and effective treatments remain

Children with ADHD who consumed LC-PUFAs mostly from fish oil had significant improvements in their ADHD behaviors–inattention, hyperactivity and impulsiv-ity–after 15 weeks. Continued supplementation for another 15 weeks led to further improve-ments without adverse effects.


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elusive. As the authors note, it may take 2 to 3 months or longer for benefits to become apparent. Considering the alternatives, patience seems a low hurdle.

Sinn N, Bryan J. Effect of supplementation with polyun-saturated fatty acids and micronutrients on learning and behavior problems associated with child ADHD. J Dev Behav Pediatr 2007;28:82-91.

Low n-3 LC-PUFA Status Might Be Linked to Mood and Behavior in Healthy AdultsThe involvement of omega-3 long-chain polyunsatu-rated fatty acids (n-3 LC-PUFAs) in brain structure and function, particularly in cell signaling, cognition and behavior, provides a plausible basis for considering the involvement of these PUFAs in psychological and psychi-atric disorders. Although the brain is highly enriched in docosahexaenoic acid (DHA), an n-3 LC-PUFA, western diets contain predominantly omega-6 (n-3) PUFAs, with as little as one-tenth as much coming from n-3 PUFAs, most of which is alpha-linolenic acid. Observational studies have correlated low intakes of n-3 LC-PUFAs with higher prevalence of depression, hostility and bipolar disorder and other mood disorders. Some, but not all, intervention studies have reported reduced psychosocial symptoms with the consumption of n-3 LC-PUFAs. There is little information about the behavioral effects, if any, of low n-3 LC-PUFA status in people with-out psychiatric symptoms.

To determine whether n-3 LC-PUFAs are related to psycho-logical and behav-ioral characteristics in healthy adults, Sarah Conklin and colleagues at the University of Pittsburgh examined

serum fatty acids and psychological assessment scores in community volunteers with hypercholesterolemia par-ticipating in the Cholesterol and Risk Evaluation Project. Participants, aged 35 to 70 years (average 55 years) and 49% male, were randomly assigned to consume a pla-cebo or 10 mg or 40 mg of simvistatin (for cholesterol reduction) for 6 months. Participants were excluded if they consumed fish oil, any medications for lipid or psy-chiatric disorders or had a history of coronary heart dis-ease, diabetes, cancer, psychiatric illness or other serious ailments. Psychological assessments included the Beck Depression Inventory, Barratt Impulsiveness Scale and the NEO-Five Factor Inventory, which assesses 5 dimen-sions of adult personality on a 5-point rating scale. Baseline data for the first 105 participants were available for the present study.

The relationship between fatty acid concentrations, which covered up to a 2-fold range (Table), and psycho-logical assessment scores was evaluated in multivariate analysis. A few fatty acid measurements and psychologi-cal scores were related to gender, race and age, so these variables were included as covariates in the analyses.Statistically significant correlations were observed between low serum eicosapentaenoic acid (EPA) or DHA concentrations and higher Beck’s Depression scores. These n-3 LC-PUFAs were also negatively asso-ciated with neuroticism and the Barratt’s cognitive impulsivity score. In contrast, high DHA levels were associated with higher scores for agreeableness on the NEO-Five Inventory. In multivariate regression analy-sis, the investigators determined that for a 1 standard deviation increase in serum DHA concentration, the odds of depressive symptoms by the Beck’s Depression Inventory decreased by over 50%.

These observations in a hypercholesterolemic, but oth-erwise healthy, adult population suggest that lower serum concentrations of n-3 LC-PUFAs are associated with scores at the lower end of psychological assess-ments of personality, depression and impulsivity. In con-trast, higher serum DHA was associated with the NEO-Five Inventory measure of agreeableness. These asso-ciations suggest a continuum from the normal range to more severe assessments in psychiatric disorders that inversely tracks n-3 LC-PUFA concentrations in serum.

Finding these associations in serum avoids the problems associated with dietary assessment, but they are limited by the constraints of all observational studies and may not be causally related. Further, it is unclear whether personality and mood traits affect food choices or vice versa. There is evidence to support both possibilities.

Conklin SM, Harris JI, Manuck SB, Yao JK, Hibbeln JR, Muldoon MF. Serum omega-3 fatty acids are associated with variation in mood, personality and behavior in hyper-cholesterolemic community volunteers. Psychiatr Res 2007

Table. Participant serum PUFA concentrations

Fatty acid µg/mL Median Interquartile range (25%-75%)n-3 PUFAs ALA 19.5 13.8 – 27.5 EPA 18.1 12.7 – 24.1 DHA 46.4 36.9 – 57.9n-6 PUFAs LA 971.2 843.3 – 1120.6 AA 255.1 255.1 – 296.7

Does low n-3 LC-PUFA status affect the personality or behavior of healthy adults without psychiatric problems? A University of Pittsburgh study suggests it might.


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Volume of Key Brain Regions Associated with Omega-3 PUFA ConsumptionScientists ingeniously pursue ways of measuring what is happening in the living brain without actually peer-ing inside. One technique, well adapted to examining soft tissue, is magnetic resonance imaging (Figure). Three-dimensional images of the brain are created from radio waves sent through the brain in a magnetic field. Sensors read the signals and a computer con-structs an image from the information it receives. Differences in local con-centrations of tissue can be measured using voxel-based morphometry, a technique that normalizes the images from each par-ticipant for a specified tis-sue location so they can be measured and compared.

The brain accumulates doc-osahexaenoic acid (DHA) during gestation, especially during the last trimester and through the first 2 to 10 years after birth. Enrichment of DHA coincides with the rapid formation of synapses, neurite growth and the development of dendrites. DHA deficiency reduces learn-ing ability, impairs spatial task performance and reduces memory. Restoration of DHA improves brain function and cognition in deficient and disease states. DHA appears to have critical functions in protecting neurons against oxidative stress, degenerative disease and inflammatory damage in Alzheimer’s disease.

Low intake or status of long-chain omega-3 polyunsatu-rated fatty acids (n-3 LC-PUFAs) has been associated with cognitive and behavioral disorders in humans and DHA-linked deficits have been reported in Alzheimer’s disease. However, changes in living tissue in the brain regions associated with functional impairments, such as the hip-pocampus, amygdala and anterior cingulated cortex, have not been ascertained. The first step toward such measure-ments has now been reported by Sarah Conklin and col-leagues at the University of Pittsburgh, USA.

Conklin’s team rea-soned that regions of the brain sensi-tive to n-3 LC-PUFAs might differ in vol-ume, according to an individual’s con-sumption of these PUFAs. To find out,

the investigators recruited 55 participants (average age 45 years) from the Adult Health and Behavior Project, a registry of behavioral and biological traits in a com-munity sample of non-patient, middle-aged volunteers. Participants were in good health, free of medical con-ditions affecting cerebral blood flow and metabolism, alcohol or drug abuse and not taking omega-3 supple-ments or psychotropic, hyperlipidemic or cardiovascular medications. Structural MRI images of the head were taken of each participant, with gray matter volume of the amygdala, hippocampus and anterior cingulated cortex measured using voxel-based morphometry.

Data from two 24-hour diet recall interviews were used to estimate the daily intake of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The investiga-tors assessed the relationships between tertiles of EPA and DHA intake and gray matter volume in the specified brain areas using multiple linear regression analysis, con-trolling for age, sex and total gray matter volume.

Three categories of EPA and DHA closely resembling tertiles of intake were low (0-20 mg/day), medium (25-70 mg/day) and high (80-1,600 mg/day), with 16, 21 and 18 participants in each group, respec-

tively. Multiple linear regression analysis showed a sig-nificant association between EPA and DHA consump-tion and gray matter volume in the subgenual anterior cingulated cortex (P=0.04) and in an overlapping area of the right amygdala (P=0.03) and right hippocampus (P=0.05). There was no association between EPA and DHA intake and whole brain analysis.

Implications of these observations remain to be clari-fied. The anterior cingulated cortex is associated with cognitive function, transient mood changes, depression, anxiety disorders and the regulation of autonomic pro-cesses. These functions may be impaired in people with low DHA status. Increased prevalence of depression and bipolar disorder has been reported in populations with low seafood consumption and, in some studies, patients with these disorders have had improvements in their symptoms following the consumption of n-3 LC-PUFAs.The amygdala is involved in emotional feelings and behaviors related to fear and anger, as well as the mem-ory of emotional reactions. Emotions such as hostility, aggression and harming oneself are affected by low n-3 LC-PUFA status. Increased consumption of n-3 LC-PUFAs has been reported beneficial in patients with recurrent

Conklin and associates reasoned that regions of the brain sensitive to n-3 LC-PUFAs might differ in volume, according to an individual’s consumption of these PUFAs.

Figure. Magnetic resonance imaging machine. Image courtesy of Siemens AG. Regression analysis showed

a significant association between level of EPA+DHA consumption and gray mat-ter volume in the subgenual anterior cingulated cortex, amygdala and hippocampus.


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self-harm, aggression and hostility.

The hippocampus, seat of memory and spatial naviga-tion, is also the primary region affected by Alzheimer’s disease. It is plausible that higher brain concentrations of EPA and DHA, particularly DHA, which might be associated with protection against memory loss, neu-rodegeneration and lower chance of mood disorders, would also be reflected in increased brain volumes in areas linked to these functions. In an aged, ischemic and diseased brain, n-3 LC-PUFAs have neuroprotective properties. Conklin’s observations are among the first in humans to link a physiological parameter (volume) of key functional areas of the brain with dietary intake of EPA and DHA. They add to a consistent pattern in which dietary n-3 LC-PUFAs contribute to brain structure and function that becomes disordered when these key com-ponents are too scarce.

This study suggests that scientists might have another tool for exploring relationships between interventions and outcomes in health and disordered conditions. Direct links between brain volume in key brain regions, function and treatment interventions may make having a swelled head not such a bad thing after all.

Conklin SM, Gianaros PJ, Brown SM, Yao JK, Hariri AR, Manuck SB, Muldoon MF. Long-chain omega-3 fatty acid intake is associated, positively, with corticolimbic gray matter volume in healthy adults. Neurosci Lett 2007;21:209-212.

Kotani S, Sakaguchi E, Warashina S, Matsukawa N, Ishikura Y, Kiso Y, Sakaakibara M, Yoshimoto T, Guo J, Yamashima T. Dietary supplementation of arachidonic and docosahexaenoic acids improves cognitive dysfunc-tion. Neurosci Res 2006;56:159-164.

■ CLINICAL CONDITIONS

Alzheimer’s DiseaseNovel Effects of Dietary DHA and Omega-6 DPA on Pathologies in Alzheimer’s ModelThe underlying pathology of Alzheimer’s disease

involves the extra-cellular accumula-tion of abnormal amyloid-β protein in the hippocam-pus and neocor-tex, which forms plaques. These may also appear inside

the neurons. A second characteristic is the develop-ment of neurofibrillary tangles inside neurons result-ing from the buildup of hyperphosphorylated tau protein. The disease entails progressive memory loss, cerebral atrophy and several other abnormalities.

Various environmental adjustments, including diet, may slow disease progress. Low levels of docosahexaenoic acid (DHA), a long-chain omega-3 polyunsaturated fatty acid (n-3 LC-PUFA) have been associated with the likelihood of developing the condition and disease progression, and increased DHA intake may slow its progress if the disease is detected very early. The brains of Alzheimer’s patients have less DHA than normal con-trols, lower concentrations of neuroprotectin D1, which is synthesized from DHA, and higher concentrations of lipid peroxidation products. DHA supplementation can reverse some of the amyloid pathology in a mouse model of the disease, but much remains to be learned about DHA and other dietary substances in Alzheimer’s pathology. Whether omega-6 (n-6) PUFAs affect the disease is not well understood, but reduced n-6 PUFA concentrations in Alzheimer’s as compared to control patients have been reported.

A group of researchers at the University of California in Irvine investigated the effects of various dietary LC-PUFAs on Alzheimer’s pathologies in a transgenic mouse model of the disease that exhibits both amyloid-β and tau protein abnormalities. Each diet contained 5% fat. LC-PUFA content of the diets were: none (control), 1.3% DHA, 1.3% DHA plus 0.5% docosapentaenoic acid (DPAn-6), and 1.3% DHA plus 0.5% arachidonic acid (AA). Test diets were constant in DHA, total n-6 and n-3 PUFAs and percentage of saturated, monounsatu-rated and PUFAs. Investigators were double-blinded to the diets and groups throughout the study. Diets were consumed by groups of 3-month-old animals for 3, 6 and 9 months.

Analyses included fatty acid composition of red blood cells, total brain lipids, concentrations of soluble and insoluble amyloid-β protein, and of degradation prod-ucts of amyloid-β, secretase enzyme levels, presenilin concentrations and accumulation of tau protein and phosphorylation of tau, all in relation to dietary treat-ment and time. Histopathology was also recorded for each group at each 3-month interval.

Total brain DHA levels increased 1 to 3 weight percent-ages in all PUFA-supplemented diets, with the great-est increase in mice supplemented only with DHA. The increase in DHA was at the expense of AA in all 3 PUFA-enriched diets. In animals consuming DPA(n-6), brain content of this fatty acid increased to more than twice

DHA can reverse some of the pathology of Alzheimer’s disease in animal models, but how it does so is unknown. Whether and how omega-6 PUFAs affect the disease is also poorly understood.


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that in control mice, but DPA was very low in red blood cells. Brain content of alpha-linolenic acid was very low (<0.5%) and EPA was only slightly higher. There was some evidence of retroconversion of DHA to EPA in the DHA-only supplemented group.

The accumulation of soluble and insoluble amyloid-b proteins 40 and 42 in the whole brain was measured after 3, 6, and 9 months of dietary treatment. At 3 months, soluble amyloid-β levels were significantly lower in all PUFA groups compared with controls, sug-gesting that DHA was responsible (Figure 1). Insoluble protein was low in all groups because the animals were young. Staining of amyloid-β in the neurons of the hippocampus and amygdala was also reduced in these treatment groups.

After 6 months, soluble amyloid-β was significantly reduced in the DHA and DHA-DPA treatment groups,

but was unchanged in the control and DHA-ARA ani-mals. Insoluble amyloid-b was unchanged in the treat-ment groups, but insoluble amyloid-β42 began to accu-mulate as the disease became established.

After 9 months, only the animals fed just DHA had significantly reduced soluble amyloid-β, whereas the other treatment groups had protein levels similar to the controls. Insoluble amyloid-β40 and 42 proteins were unaffected by diet and had increased in all groups, with the largest increase in amyloid-β42 occurring in the DHA+DPA group.

These observations indicate that DHA supplementa-tion significantly reduces the accumulation of soluble amyloid-β, but that the effect is abolished in the presence of other n-6 LC-PUFAs. In a separate series of experiments, the investigators evaluated whether the reduced levels of soluble amyloid-β resulted from

Figure 1. Levels of soluble and insoluble beta-amyloid in whole brains of Alzheimer mice fed diets with DHA or DHA plus DPA or ARA for 3, 6, and 9 months. Reproduced from J Neurosci 2007;27:4385, ©2007 by the Society for Neuroscience.


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decreased production or increased degradation of the amyloid-b precursor protein, but were unable to con-firm any enzyme, lipoprotein or carrier protein changes to account for the effect of DHA.

Further examination focused on the proteins involved in the release of amyloid-β precursor protein from the neuronal cell membrane. Two secretase complexes are involved in this process and in one, γ-secretase, 2 constituent proteins presenilin 1 and presenilin 2 are needed for the successful release of amyloid-β. The investigators observed that all 3 PUFA diets sig-nificantly reduced presenilin-1 compared with controls after 3 months of the diets, but had no effect on other γ-secretase complex proteins (Figure 2). The reduction in presenilin-1 correlated with the reduced soluble amyloid-β levels observed after 3 months of treat-ment. After 6 months of dietary treatment (9 months of age), presenilin-1 levels were significantly decreased in the DHA-only group, and at 12 months of age, there were no differences in presenilin levels among any treatment groups. Presenilin-1 levels decreased with longer treatment and occurred prior to changes in soluble amyloid-β.

The research team also examined steady-state levels of tau protein in hippocampal sections. As with the accumulation of soluble amyloid-b, all 3 diets reduced tau protein after 3 months. After 6 months, only the DHA-only and DHA+DPA diet groups had reduced tau protein accumulation. After 9 months, only the DHA-only group had significantly lower tau and amyloid-β levels compared with the controls. This suggests a direct relationship between soluble amyloid-β levels and tau accumulation.

Interestingly, when the investigators explored the treatment effects on the phosphorylation of tau, an event that precedes the accumulation of tau neuro-fibrillary tangles, they found the greatest reduction in altered tau proteins in the DHA+DPA diet group and to a lesser extent in the DHA-only group com-pared with the controls (Figure 3). DHA+DPA was the most effective treatment in preventing both conformational changes and phosphorylation of tau. These effects were independent of soluble amyloid-β. This novel observation suggests that DHA can reduce soluble amyloid-β and tau protein, but that DPA inhibits the progression of tau to neurofibrillary tangles. What this means for the clinical pathology of Alzheimer’s disease in humans remains speculative.

The authors drew several conclusions. First is that the effect of DHA on amyloid-b levels probably occurs by suppressing γ-secretase activity, as products of the other secretases, α- or β-secretase, were unaffected by the diets. This conclusion accords with findings of oth-ers who observed no differences in amyloid-β precursor protein processing with increased DHA. The investiga-tors suggest that the effect on γ-secretase is mediated by reductions in presenilin-1, but cannot rule out the involvement of other proteins in this secretase com-plex. The ability of DHA to reduce amyloid-β and tau

Figure 2. Steady state levels of presenilin-1 and nicastrin γ-secretase proteins in whole brains of Alzheimer mice after 3 (top) 6 and 9 months of PUFA diets (bottom) when mice were 6, 9 and 12 months of age. Reproduced from J Neurosci 2007;27:4385, ©2007 by the Society for Neuroscience.

Figure 3. Quantification of staining intensity of phosphorylated tau proteins from hippocampus of Alzheimer mice fed PUFA diets for 9 months. Reproduced from J Neurosci 2007;27:4385, ©2007 by the Society for Neuroscience.


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protein buildup weakens with time, possibly because of the toll of their gradual accumula-tion. The study also provided evidence that dietary DHA reduced intraneuro-nal accumulation of amyloid-β, although the significance of this observation is unclear. Amyloid plaque is poorly cor-related with cogni-

tive decline, but levels of soluble amyloid-β are associ-ated with loss of cognition. Reductions in soluble amy-loid could be important in slowing disease progression.

The accumulation of insoluble amyloid-β aggregates was unaffected by dietary DHA and the authors specu-late that the dynamics of these assemblies may be insensitive to DHA or that in aging, the brain allows more of these aggregates to form.

DHA reduced the accumulation of tau protein, pos-sibly because of the reduced buildup of soluble amyloid-β. Levels of tau were strongly correlated with levels of soluble amyloid-β at all time points. But DPA(n-6) enhanced the reduction of tau protein compared with DHA-only and inhibited tau phos-phorylation, a step leading to the formation of neu-rofibrillary tangles.

Interestingly, dietary DHA with DPA(n-6) or AA initially reduced soluble amyloid-β levels, but with time the efficacy of these treatments diminished. After 6 months on the diets, only DHA by itself reduced amyloid-β. How the relationships among these fatty acids operate in Alzheimer’s disease in humans remains to be eluci-dated. These observations occurred with experimen-tal diets having similar amounts of n-6 and n-3 PUFAs compared with a control diet, similar to western diets, which have 10 or more times as much n-6 as n-3 PUFAs. Nevertheless, these elegant studies extend the evidence for DHA deterring or slowing Alzheimer’s disease, sug-gest how it might do so, and introduce a new-comer to the scene, DPA(n-6).

Green KN, Martinez-Coria H, Khashwji H, Hall EB, Yurko-Mauro KA, Eillis L, LaFerla FM. Dietary docosahexaenoic acid and docosapentaenoic acid ameliorate amyloid-beta and tau pathology via a mechanism involving presenilin 1 levels. J Neurosci 2007;27:4385-4395.

Age-Related Macular DegenerationBoosting DHA and Limiting Arachidonic Acid May Guard Against Advanced AMDOne of the vicissitudes of aging is the diminution of sen-sory and physical function. Glasses, hearing aids and canes provide useful compensation, but prevention is even bet-ter. Among the disabilities of aging is impaired visual function from cataracts, glaucoma, diabetic retinopa-

thy and age-related macular degenera-tion (AMD), to name the most common. AMD is responsible for the largest share of irreversible vision loss in the U.S. in people over the age of 65. Some 1.75 mil-

lion individuals in the U.S. have AMD and another 7 mil-lion are at substantial risk of developing the condition.

Against the rising tide of AMD after age 60 is the good news that certain dietary features may prevent or retard the progress of the condition. High doses of vita-mins C, E and beta-carotene with zinc have been shown to reduce the risk of developing advanced AMD. Long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFAs) are candidates for reducing the chance of devel-oping AMD and retarding its progress to the advanced stage. Fish consumption is also associated with reduced risk of AMD.

The longitudinal Age-Related Eye Disease Study (AREDS) in the U.S. is examining several nutritional factors in the development of eye diseases in people 55 to 80 years of age. The study has already confirmed the value of high-dose antioxidant vitamins and zinc in AMD and will be examining the effects of n-3 LC-PUFA and xan-thophyll interventions on the progression of AMD. In this report, the AREDS investigators used a case-control approach to evaluate the relationship between dietary lipids and the severity of AMD in patients recruited into the AREDS study.

Study participants were divided into 4 AMD catego-ries according to the size and extent of drusen (tiny deposits in the retina or optic disc) in each eye, clini-cal symptoms of AMD and visual acuity. At enrollment, participants completed a food frequency questionnaire to assess how often they had consumed various foods during the past year. From these data, the investigators determined the consumption of classes and individual fatty acids. Comparisons were made between the high-est and lowest quintiles of nutrient or food consumed. The AREDS team used logistic regression analysis with

This study provides evidence that DHA reduces amyloid-b by suppressing g-secretase activity. The effect is mediated by reductions in one of the secretase complex proteins, presenilin-1. The effect of DHA in reducing soluble amyloid-b weakens with time. Omega-6 DPA enhanced the reduction of tau protein observed with DHA by inhibiting tau phosphorylation.

Against the rising tide of age-related macular degeneration after age 60 is the good news that certain dietary features may prevent or retard the progress of the disease. Eating fish is one of them.


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adjustment for multiple variables such as age, sex, energy intake and demographic factors to determine the relationship between dietary factors and severity of AMD, expressed as odds ratios. The reference group consisted of participants without drusen or with non-extensive small drusen. This report includes observa-tions from 4,519 participants aged 60 to 80 years.

In a multivariate analysis, intakes of docosahexaenoic acid (DHA) and total n-3 PUFAs were inversely and signif-icantly related to the most severe classification of AMD, the neurovascular form (Table). In contrast, consump-tion of monounsaturated and saturated fatty acids was associated with increased risk of neurovascular AMD. Cholesterol intake was positively associated with the intermediate grades (large drusen) of the disease.

When the relationships between neurovascular AMD and fatty acid intakes were examined by quintiles of intake, DHA and total n-3 PUFAs remained significantly associated with lower risk (P for trend = 0.004 and 0.01, respectively). In contrast, arachidonic acid was signifi-cantly related to increased risk of the most advanced AMD (P for trend = 0.03), but there was no significant trend for greater risk with increasing intakes of saturated or monounsaturated fatty acids and of cholesterol.

Total fish consumption of more than 2 servings/week and the intake of baked or broiled fish were inversely and significantly associated with lower risk of neurovas-cular AMD (P for trend = 0.01 and 0.02, respectively).

These results support current evidence that diets high in DHA, and to a lesser extent eicosapentaenoic acid (EPA),

significantly lower the chance of developing advanced AMD. In terms of the dinner plate, the amount of fish providing the greatest protection was equivalent to 2 fish meals/week (40% lower risk) or one medium serv-ing of baked or broiled fish/week (35% lower risk). These findings are consistent with recommendations from the American Heart Association to consume 2 fish meals/week, preferably of fatty fish, for cardiovascular benefits.

The data in this study identified high intakes of ara-chidonic acid, found mainly in meats, poultry, eggs and fish, with signifi-cantly higher risk (1.5 times greater) of advanced AMD. This determination is consistent with a

previous epidemiological report in which consump-tion of n-3 LC-PUFAs or fish was associated with lower risk of AMD only when the diet was low in linoleic acid. However, both DHA and arachidonic acid are major structural LC-PUFAs in the retina. This report’s observations imply that a relative dietary imbalance of these LC-PUFAs may contribute to AMD pathology. It is also noted that n-3 LC-PUFA or fish intakes were not associated with reduced risk of AMD in its earliest stages. Bear in mind, too, that other factors such as smoking, genetics, high body mass index and presence of other diseases increase the chance of developing AMD. Seeing your way to eating fish twice a week, however, seems a simple way to keep both eyes and heart uncluttered.

SanGiovanni JP, Chew EY, Clemons TE, Davis MD Ferris FL, Gensler GR, Kurinij N, Lindblad AS, Milton RC, Seddon JM, Sperduto RD, Age-Related Eye Disease Study Research Group. The relationship of dietary lipid intake and age-related macular degeneration in a case-control study: AREDS Report No. 20. Arch Ophthalmol 2007;125:671-679.

Bone Mineral DensityLong-Chain Omega-3s Linked to Greater Bone Mineral Density in Young MenInterest in halting the deterioration of bones in post-menopausal women and older men is of practical and pressing concern as western populations age. Loss of bone mass and the onset of osteoporosis, a disease affecting some 10 million people in the U.S., are key causes of the 1.5 million bone fractures that occur in the U.S. every year.

Table. Odds ratios of neurovascular AMD by highestversus lowest quintiles of fatty acids intake*

Fatty acid Odds ratio, highest vs P lowest intake (95% CI)n-3 PUFAs ALA 1.05 (0.74-1.47) NS EPA 0.72 (0.51-1.01) ≤ 0.05 DHA 0.60 (0.42-0.85) ≤0.01 Total n-3s 0.63 (0.45-0.89) ≤0.01n-6 PUFAs LA 1.09 (0.77-1.54) NS ARA 1.09 (0.77-1.54) NSMonounsaturates 1.80 (1.27-2.56) ≤0.01Saturates 1.56 (1.09-2.23) ≤0.01

*Adjusted for multiple variables including total energy intake, sex, body mass index, education, refractive error, race, smoking history, hypertension and lens opacity.

These results support current evidence that diets high in DHA, achieved with 2 fish meals/week, cut the risk of advanced AMD by as much as 40%. Limiting the intake of arachidonic acid from meats, poultry and eggs may also protect against AMD.


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Strategies to improve bone health in people over the age of 50 involve diet, physical activity, smoking cessa-

tion and medication to increase calcium deposition and slow bone loss. Thus, con-trolling osteoporo-sis requires a multi-pronged approach.

Dietary components important for good bone health include calcium, vitamins D and K, abundant

intake of fruits and vegetables, moderate protein con-sumption, and limiting vitamin A consumption to no more than 5,000 International Units/day. Long-chain polyunsaturated fatty acids (LC-PUFAs) might find their way to this list.

Studies in animals and cultured cells have demonstrated that LC-PUFAs and their eicosanoid derivatives, such as prostaglandin E2, affect bone metabolism, cell pro-liferation and the activity of osteoblasts (bone-form-ing cells) and osteoclasts (bone-degrading cells). The content and relative proportion of omega-3 (n-3) and omega-6 (n-6) LC-PUFAs affected calcium and zinc accretion in piglets and bone formation in rats, with greater amounts of n-3 LC-PUFAs favoring bone forma-tion. Fish oil was associated with less bone resorption in rats with induced periodontal disease. In aging male rats, fish oil-rich diets were associated with less bone loss compared with safflower oil-rich diets or one con-taining both safflower and fish oil. Rats fed diets high in n-3 LC-PUFAs had higher bone peak load and stiff-ness compared with animals fed control or high n-6 PUFA diets. These examples suggest why interest in the effects of LC-PUFAs on bone has intensified.

Human studies are scant, but accumu-lating. A diet high in alpha-linolenic acid, a plant-based n-3 PUFA, reduced concentrations of a marker of bone resorption in middle-aged, overweight,

mildly hypercholesterolemic volunteers. In infants, cord blood arachidonic acid content was positively correlated with whole body bone mineral content, but maternal blood DHA was negatively associated with infant lumbar spine and femur bone mineral content. In older adults,

an increasing ratio of dietary n-6 to n-3 PUFAs was signif-icantly associated with lower hip bone mineral density. In surgical patients, prostaglandin E1 significantly reduced the decline in bone mineral density that usually follows liver transplantation. EPA significantly reduced the com-plications of bone marrow transplantation and improved patient survival.

Reports on eicosapentaenoic acid (EPA), an n-3 LC-PUFA, have been inconsistent, with detrimental effects in ovariectomized rats, but favorable effects on bone mineral density when combined with gamma-linolenic acid and consumed for 36 months by post-menopausal women with osteoporosis. Because of EPA’s strong anti-inflammatory effects, it has been difficult to dis-tinguish whether its effects on markers of bone turn-over are a result of changes in inflammation and cyto-kines or direct effects on bone cells. Other LC-PUFAs may be involved, too. Dietary conjugated linoleic acid was positively associated with higher bone mineral density in post-menopausal women. Another possibil-ity is increased calcium absorption with LC-PUFAs, as has been reported in rats.

In this report, Magnus Hogstrom and colleagues at Umea University in Sweden report findings from an 8-year study on serum fatty acids and bone mineral density in young men. From a sample of 95 adolescent males aged 17 years enrolled initially, 78 were available for assess-ment and blood sampling 6 years later, and 73 of those had a bone scan again after 8 years. Bone mineral den-sities of the total body and right hip were determined using a dual-energy X-ray absorptiometer. Density of the spine was derived from the total body scan. Fatty acids were measured in serum phospholipids.

Dietary components important for good bone health include calcium, vitamins D and K, abundant intake of fruits and vegetables, moderate protein consumption, and vitamin A limited to 5,000 IU/day. Long-chain polyunsaturated fatty acids (LC-PUFAs) might find their way to this list.

Studies in animals and a small number in humans suggest that n-3 LC-PUFAs have favorable effects on markers of bone health. Other LC-PUFAs, such as omega-6s may modify bone turnover.

Table. Pearson’s correlation coefficients between serum phospholipid fatty acids and bone mineral density in young men at age 17 and the difference in bone density between age 17 and 23.

Total BMD Spine BMDFatty acid Age 17 Change Age 17 Change 17-23 yr 17-23 yrAA 0.17 0.12 0.18 0.25*EPA 0.18 0.04 0.15 0.16DHA 0.32** 0.10 0.30** 0.26*Total n-3 LC-PUFAs 0.27* 0.10 0.25* 0.26*Saturates 0.21 0.04 0.13 0.05Monounsaturates -0.25* -0.18 -0.21 -0.21Polyunsaturates 0.09 0.14 0.10 0.16

*P<0.05, **P<0.01


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Total body bone mineral density at the first follow-up (age 23 years) was significantly and positively associ-ated with serum docosahexaenoic acid (DHA) and total n-3 LC-PUFAs and negatively associated with oleic acid and total monounsaturated fatty acids (Table). Spine density was related to DHA and total n-3 LC-PUFAs. The increase in bone density between the ages of 17 and 23 was significantly related to serum arachidonic acid, DHA and total n-3 LC- PUFAs, but negatively with the ratio of n-6 to n-3 PUFAs. There were no significant associations between hip bone density and any serum fatty acid, or between bone densities at any loca-tion at age 25 and fatty acids. When the relationships between fatty acids and bone densities were evalu-ated by linear regression analysis adjusted for weight, height and physical activity, total body bone density was significantly related to EPA, DHA and total n-3 LC-PUFAs at age 23.

This study provides evidence that the accumulation of bone mineral den-sity from age 17 to 23 years in young men is associated with the consump-tion of n-3 LC-PUFAs. By measur-ing serum fatty acids rather than assessing dietary intake, the investi-gators had a more reliable indicator

of LC-PUFA status. As the authors noted, the par-ticipants were recruited from schools and sports clubs and were perhaps more active than young men drawn from the general population. At ages 17 and 23, the participants averaged 7 and 5 hours of activ-ity/week and physical activity increases bone mineral density. One can speculate that increased intake of n-3 LC-PUFAs might enhance peak bone density in young women, who are at greater risk of osteopo-rosis after menopause, and hence, might benefit substantially from such a dietary change. It would be useful to find out.

Hogstrom M, Nordstrom P, Nordstrom A. n-3 fatty acids are positively associated with peak bone mineral density and bone accrual in healthy men: the NO

2 Study. Am J Clin

Nutr 2007;85:803-807.

Vanek C, Conner WE. Do n-3 fatty acids prevent osteopo-rosis? [Editorial] Am J Clin Nutr 2007;85:647-648.

FRONTIERSLipid Rafts in Immune and Cancer CellsSooner or later, the exploration of how long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFAs) work takes one to the cell membrane where eicosap-entaenoic acid (EPA) and docosahexaenoic acid (DHA) are stashed in phospholipids. Inserted into the mem-brane bilayer are molecules of cholesterol, proteins (e.g., enzymes, hormone receptors), sphingolipids and others. Cell membranes are highly active in cellular processes, controlling the flux of substances as large as proteins and as small as ions and the activation of its protein constituents. Messages from events occurring at or in the membrane are relayed to other molecules on either side of it, initiating a cascade of communica-tion known as cell signaling. n-3 LC-PUFAs participate in these processes.

Membrane composition is heterogenous and dynamic, with lipids and proteins moving in and out, being mod-ified or changing locations. Membranes have regions that are comparatively rigid and sections of substantial fluidity. Regions comprised of tightly packed compact lipid chains, such as glycosphingolipids, cholesterol, phospholipids and proteins constitute microdomains known as lipid rafts (Figure). These are believed to serve as platforms for protein activity. Lipid rafts, as described by Kai Simons, who first proposed their exis-tence, are “dynamic assemblies of proteins and lipids that float freely within the liquid-disordered bilayer of cellular membranes, but can also cluster to form larger, ordered platforms.” Rafts have lipids with saturated fatty acids and cholesterol that pack tightly, whereas the surrounding membrane lipids are more fluid and contain highly unsaturated fatty acids, such as LC-PUFAs (Figure 2). Simons suggested that cholesterol serves as a spacer between the sphingolipid hydrocar-bon chains and as a glue to keep the rafts together. It is the task of cholesterol to modulate the physical properties of the membrane.

Lipid rafts are involved in cell signaling, allergic responses, trafficking of membrane components, patho-gen activity (e.g., prion, viruses) and many diseases, including atherosclerosis, Alzheimer’s disease, muscular dystrophy, osteoarthritis, autoimmune disease, sepsis and many infectious agents.

Because lipid rafts are sites of critical cellular activity, it is of interest to find out how membrane enrichment with LC-PUFAs, especially those of the n-3 family, affect lipid raft composition and function. LC-PUFAs have been reported to trigger the formation of rafts, change the lipid composition of rafts, inhibit T cell signal transduction, displace raft proteins and lipids

This study provides evidence that the accumulation of total body bone mineral density from age 17 to 23 years in young men is associated with the consumption of n-3 LC-PUFAs. One can speculate that increased intake of n-3 LC-PUFAs might enhance peak bone density in young women who might benefit substantially from such a dietary change.


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and remodel raft fatty acid composition. Altering the LC-PUFA composition of the membrane would favor the formation of PUFA-rich domains (not rafts) and alter the composition of lipid rafts.

n-3 LC-PUFAs incorporated into membrane phospho-lipids markedly affect the physical characteristics of the membrane, reduce the solubility of membrane cholesterol and enhance the formation of cholesterol and sphingomyelin-rich lipid rafts. As summarized by Stillwell, it is DHA’s “aversion to cholesterol” that repels the DHA-containing phospholipids away from cholesterol. This results in the separation of DHA- and cholesterol-rich and sphingolipids-poor liquid disor-dered domains, i.e., membrane sections that are not rafts, from the sphingolipids- and cholesterol-rich domains that form rafts. Because these segments of the membrane differ widely in physical characteristics, the location of signaling proteins is altered, which in turn, affects cell signaling and function.

The paper cited below by Siddiqui and colleagues reviews numerous examples where cell signaling in lipid rafts is modified by the EPA- or DHA-enrich-ment of membranes. Inflammatory responses and cancer cells are the most widely studied systems. It is now understood that partial disorganization of lipid rafts due to n-3 LC-PUFAs underlies the alterations in immune cell function that occurs with fish oil con-sumption. Increased n-3 LC-PUFA concentration inhib-its T-cell activation, decreases the expression of CD4 and CD8 glycoproteins on the surface of T-cells that determine which types of cells bind to T-cells, depletes T-cell rafts of sphingolipids, alters their phospholipid composition and displaces certain membrane proteins from lipid rafts–all of which disrupt T-cell signaling and prevent activation. Even when activated, EPA-enriched cells have impaired localization of several molecules (e.g., actin) and reduced the surface expres-sion of major histocompatibility complex molecules,

which interferes with antigen/antibody responses.

n-3 LC-PUFAs also affect B lymphocytes. The surface protein CD20 is associated with lipid rafts and in pro-liferating cells it is expressed diffusely over the cell surface. However, with n-3 LC-PUFAs, CD20 aggregates in the lipid rafts that become consolidated into large patches. Siddiqui and colleagues suggest that priming B lymphocytes with n-3 LC-PUFAs may improve binding to CD20. They suggest the possibility of CD20-bind-ing antibodies carrying therapeutic agents that might target the cell more effectively and induce cell death, providing a way to treat leukemia.

The translocation of proteins from the lipid raft to non-raft portions of the membrane was used to enhance phospholipase D activity in peripheral blood mononuclear cells. In the presence of DHA, phospho-lipase D was translocated from the lipid raft to the non-raft portion of the membrane where its activa-tor, ARF protein, resides. This resulted in activation of the enzyme.

In an analogous way, n-3 LC-PUFAs may modulate the growth and activity of cancer cells. Higher levels of saturated fatty acids and cholesterol are found in cancer cell membranes compared with healthy cells. These constituents are concentrated in lipid rafts and levels of cholesterol correlate with the progres-sion of prostate cancer. It has been suggested that n-3 LC-PUFA-rich diets may displace cholesterol and membrane receptor proteins, such as the estrogen receptor protein, from lipid rafts, thereby disrupting cell signalling pathways involved in cancer cell prolif-eration. The ability to dislodge a variety of membrane receptor proteins could explain observations that both hormone and growth factor receptors may be altered in n-3 LC-PUFA-rich cells.

Specific cancer cell receptor proteins are involved in cancer cell migration. For example, the cell surface protein CD24 is present in lipid rafts and is involved in cell adhesion. Its presence is associated with the depletion of the CXCR4 receptor protein from mem-brane rafts. CXCR4 chemokine receptors are asso-ciated with aggressive cancer and are sensitive to cholesterol content. These features suggest that n-3 LC-PUFAs may reduce cancer cell aggression by reduc-ing membrane raft cholesterol and displacing CXCR4 from the rafts. This possibility has not been investi-gated, but appears plausible from other studies in cancer cells enriched with n-3 LC-PUFAs. The authors suggest that other aspects of cancer cell function, such as cell adhesion and invasion, might be mediated by n-3 LC-PUFA effects on lipid rafts.

Figure. Schematic representation of a cell membrane showing a lipid raft enriched in cholesterol, sphingo-lipids and proteins.


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In a study of cultured breast cancer cells, Dr. Patricia Schley and colleagues at the University of Alberta, Canada, explored the impact of n-3 LC-PUFAs on cul-tured breast cancer cells, lipid raft composition, and the levels and phosphorylation of epidermal growth fac-tor receptor. As reported in T cells, exposure of breast cancer cells to EPA and DHA increased the content of these fatty acids in the membranes and phospholipids of the cell. This is the first report of n-3 LC-PUFAs being incorporated into membrane rafts (detergent-resistant membranes). Lipid rafts exhibited a reduced level of sphingomyelin (25%), an increase in ceramide–possibly cleaved from sphingomyelin–reduced cholesterol (40%) and lower concentrations of epidermal growth factor receptor. As Calder and Yaqoob point out in their com-mentary on this study, ceramide induces apoptosis and provides one explanation for how n-3 LC-PUFAs affect cell viability. Total cell epidermal growth factor receptor content was unaltered, suggesting translocation to the non-raft portions of the membrane. Whole cell phos-phorylated epidermal growth factor increased, sug-gesting that lipid rafts negatively regulate activation of this receptor. Increased growth factor phosphorylation has been associated with apoptosis, suggesting another way by which n-3 LC-PUFAs may inhibit cancer cell pro-liferation and migration.

Although many observations in cultured cells impli-cate n-3 LC-PUFAs in inhibiting the growth, spread and destruction of cancer cells, studies on the effects of dietary n-3 LC-PUFAs in humans are less clear. A recent review concluded that n-3 LC-PUFAs are unlikely to prevent cancer. However, in advanced prostate cancer, tissue LC-PUFAs were inversely related to the risk of advanced cancer and a mecha-nism for the effects of n-3 LC-PUFAs and arachidonic acid has been proposed. However, reconciling the details on cell growth and function emerging from cell studies with observations in humans will require many more bridges.

Siddiqui RA, Harvey KA, Saloga GP, Stillwell W. Modulation of lipid rafts by omega-3 fatty acids in inflammation and cancer: implications for use of lipids during nutrition sup-port. Nutr Clin Pract 2007;22:74-88.

Schley PD, Brindley DN, Field CJ. (n-3) PUFA alter raft lipid composition and decrease epidermal growth factor receptor levels in lipid rafts of human breast cancer cells. J Nutr 2007;137 548-553.

Calder PC, Yaqoob P. Lipid rafts–composition, characteriza-tion, and controversies. [Editorial] J. Nutr 2007;137:545-547.

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