Fruit and Baverage

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Linus Pauling InstituteMicronutrient Research for Optimum Health

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Fruits and Vegetables

Summary

Dietary patterns characterized by high intakes of fruits and vegetables are consistentlyassociated with significant reductions in cardiovascular disease risk. (More Information)

Although prospective cohort studies provide weak support for an association between totalfruit and vegetable consumption and cancer risk, they provide some evidence that highintakes of certain classes of fruits or vegetables are associated with reduced risk ofindividual cancers. (More Information)

The results of epidemiological and controlled clinical trials suggest that diets rich in fruitsand vegetables can help prevent bone loss. (More Information)

The results of prospective cohort studies suggest that high intakes of vitamin C andcarotenoid-rich fruits and vegetables may be associated with decreased risk of age-relatedeye diseases, such as macular degeneration or cataracts. (More Information)

Many organizations, including the Centers for Disease Control and Prevention, recommendeating a variety of fruits and vegetables daily; the recommended serving number dependson total caloric intake, which is governed by age, gender, body composition, and physicalactivity level. (More Information)

Introduction

Despite all of the controversy surrounding the optimal components of a healthy diet, there is littledisagreement among scientists regarding the importance of fruits and vegetables. The results ofnumerous epidemiological studies and recent clinical trials provide consistent evidence that dietsrich in fruits and vegetables can reduce the risk of chronic disease (1). On the other hand, evidencethat very high doses of individual micronutrients or phytochemicals found in fruits and vegetablescan do the same is inconsistent and relatively weak. Fruits and vegetables contain thousands of

biologically active phytochemicals that are likely to interact in a number of ways to prevent diseaseand promote health (2). Fruits and vegetables are rich in antioxidants, which help protect the bodyfrom oxidative damage induced by pro-oxidants. The best way to take advantage of these complexinteractions is to eat a variety of fruits and vegetables.

Disease Prevention

Cardiovascular Disease

Dietary patterns characterized by relatively high intakes of fruits and vegetables are consistentlyassociated with significant reductions in the risk ofcoronary heart disease (CHD) and stroke. A

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2/21/2012http://lpi.oregonstate.edu/infocenter/foods/fruitveg/


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meta-analysis that combined the results of 11 prospective cohort studies found that people in the90th percentile of fruit and vegetable intake (about 5 servings/day or more; for information aboutserving size, please see Examples of One Serving of Fruits or Vegetables below) had a risk ofmyocardial infarction (MI) that was approximately 15% lower than those in the 10th percentile ofintake (3). Among more than 126,000 men and women participating in the Health Professionals'Follow-up Study and the Nurses Health Study, those who consumed eight or more servings offruits and vegetables daily had a risk of developing CHD over the next 8-14 years that was 20%lower than those who consumed less than three servings daily (4). In the same cohort, the risk of

ischemic stroke (stroke caused by a reduction in blood flow to part of the brain) was 30% lower inthose who consumed at least five servings of fruits and vegetables daily than in those whoconsumed less than three servings daily (5). Based on the results of Health Professionals' Follow-up Study and the Nurses Health Study, eating one extra serving of fruits or vegetables daily woulddecrease ones risk of CHD by about 4% and decrease risk of ischemic stroke by 6%. In a meta-analysis designed to estimate the global burden of disease attributable to low fruit and vegetableconsumption, epidemiologists concluded that increasing individual fruit and vegetable consumption(excluding potatoes) up to 600 g/day (about 7 servings/day) could decrease the risk of CHD by31% and the risk of ischemic stroke by 19% (1). Three recent meta-analyses have examined fruitand vegetable consumption and risk of CHD or stroke. In a meta-analysis that included nine cohortstudies, an additional daily serving of fruit and vegetables was associated with a 4% decreased riskfor CHD (6). Another meta-analysis, which examined 12 separate studies, found that individuals

who consumed more than five daily servings of fruit and vegetables experienced a 17% reductionin risk of CHD compared to those who consumed less than three servings daily (7). In a meta-analysis of eight studies examining fruit and vegetable intake, individuals who consumed three tofive daily servings or more than five daily servings had an 11% or 26% reduction in risk of stroke,respectively, when compared to those who consumed less than three servings daily (8).

High blood pressure (hypertension) increases the risk of heart disease and stroke (9). Adding morefruits and vegetables to a sensible diet is one potential way to lower blood pressure. In the DietaryApproaches to Stop Hypertension (DASH) study, 459 people with and without high blood pressurewere randomly assigned to one of three diets: 1) a typical American diet that provided about 3servings/day of fruits and vegetables and 1 serving/day of a low-fat dairy product, 2) a fruit andvegetable diet that provided 8 servings/day of fruits and vegetables and 1 serving/day of a low-fatdairy product, or 3) a combination diet (now called the DASH diet) that provided 9 servings/day of

fruits and vegetables and 3 servings/day of low-fat dairy products (10). After eight weeks, theblood pressures of those on the fruit and vegetable diet (8 servings/day) were significantly lowerthan those on the typical American diet, while blood pressures of those on the combination (DASH)diet (9 servings/day of fruits and vegetables) were lower still. For more information on the DASHeating plan, go to the National Heart, Lung, and Blood Institute Web site.

A number of compounds may contribute to the cardioprotective effects of fruits and vegetables,including vitamin C, folate, potassium, fiber, and various phytochemicals(11). However,supplementation of individual micronutrients or phytochemicals has not generally resulted insignificantly decreased incidence of cardiovascular events in randomized controlled trials. Thus, inthe case of fruits and vegetables, the benefit of the whole may be greater than the sum of itsparts.

Type 2 Diabetes Mellitus

In addition to other complications, type 2 diabetes mellitus (DM) is associated with increased riskofcardiovascular diseasethe leading cause of death in type 2 diabetics (12). Although theevidence for a beneficial effect of a diet rich in fruits and vegetables on diabetes is not asconsistent as it is for heart disease, the results of a small number of studies suggest that higherintakes of fruits and vegetables are associated with improved blood glucose control and lower riskof developing type 2 DM. In a cohort of almost 10,000 adults in the United States, the risk ofdeveloping type 2 DM over the next 20 years was approximately 20% lower in those who reportedconsuming at least five daily servings of fruits and vegetables compared to those who reported




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consuming none (13). In another prospective cohort study that followed more than 40,000 U.S.women for an average of nine years, fruit and vegetable intake was not associated with the risk ofdeveloping type 2 DM in the entire cohort, but higher intakes of green leafy and yellow vegetableswere associated with significant reductions in the risk of type 2 DM in overweight women (14).Higher fruit and vegetable intakes were weakly associated with a reduced risk of diabetes in acohort of more than 20,000 individuals followed for 12 years (15). In a cohort of 71,346 womenparticipating in the Nurses' Health Study, total fruit and vegetable intake was not associated withrisk for diabetes, although further analysis revealed that intake of fruit or green leafy vegetables

was individually associated with a modest reduction in risk of diabetes (16). A systematic reviewand meta-analysis of five cohort studies found that fruit and vegetable intake was not associatedwith type 2 diabetes (17). However, in a cross-sectional study of more than 6,000 nondiabeticadults in the UK, those with higher fruit and vegetable intakes had significantly lower levels ofglycosylated hemoglobin (HbA1c), a measure of long-term blood glucose control (18). Possiblecompounds in fruits and vegetables that may enhance glucose control include fiber andmagnesium.

Cancer

The results of numerous case-control studies indicate that eating a diet rich in fruits and vegetablesdecreases the risk of developing a number of different types of cancer, particularly cancers of the

digestive tract (oropharynx, esophagus, stomach, colon, and rectum) and lung (19-21). The resultsof some of these studies were the foundation for the National Cancer Institutes 5 a Day program,which was aimed at increasing the fruit and vegetable consumption of the American public to aminimum of five servings daily. The current U.S. government campaign, Fruits & Veggies-MoreMatters, has replaced the "5 a Day" program. In contrast to the results of case-control studies,many recent prospective cohort studies have found little or no association between total fruit andvegetable intake and the risk of various cancers (22-44). There are several possible explanationsfor this discrepancy. Case-control studies, in which the past diets of people diagnosed with aparticular type of cancer are compared to the diets of people without cancer, are more susceptibleto bias in the selection of participants and dietary recall than prospective cohort studies, whichcollect information on the diets of large cohorts of healthy people and follow the development ofdisease in the cohort over time (45). Although prospective cohort studies provide weak support foran association between total fruit and vegetable consumption and cancer risk, they provide some

evidence that high intakes of certain classes of fruits or vegetables are associated with reduced riskof individual cancers. Higher intakes of fruits have been associated with modest but significantreductions in lung cancer risk in a pooled analysis of eight prospective cohort studies (28) and withreductions in risk of bladder cancer in some studies (46). In men, higher intakes ofcruciferousvegetables have been associated with significant reductions in the risk of bladder cancer (47) aswell as prostate cancer (48), and higher intakes of tomato products have been linked withsignificant reductions in risk of prostate cancer (49).

Osteoporosis

Several cross-sectional studies have reported that higher intakes of fruits and vegetables areassociated with significantly higher bone mineral density (BMD) and lower levels of bone resorption(loss) in men and women (50-53). In a study that followed BMD over four years, higher fruit andvegetable intakes were associated with significantly less decline in BMD at the hip in elderly menbut not elderly women (50). Fruits and vegetables are rich in precursors to bicarbonate ions, whichserve to buffer acids in the body. When the quantity of bicarbonate ions is insufficient to maintainnormal pH, the body is capable of mobilizing alkaline calcium salts from bone in order to neutralizeacids consumed in the diet and generated by metabolism (54). Increased consumption of fruits andvegetables reduces the net acid content of the diet and may preserve calcium in bones, whichmight otherwise be mobilized to maintain normal pH. However, the results of a recent placebo-controlled trial in 276 postmenopausal women suggest that supplementing the diet with alkali,either through supplemental potassium citrate or an additional 300 g/day of fruits and vegetables,did not increase BMD or blunt the age-associated bone loss over a two-year period (55). Results




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from the DASH study support a beneficial link between fruit and vegetable intake and bone health.In addition to decreasing blood pressure, increasing fruit and vegetable intakes from about 3 to 9servings daily decreased urinary calcium loss by almost 50 mg/day (10) and lowered biochemicalmarkers of bone turnover, particularly bone resorption, including serum levels of C-terminaltelopeptide of type 1 collagen (56). Taken together, the results of epidemiological studies andcontrolled clinical trials suggest that a diet rich in fruits and vegetables can help prevent bone loss,although the specific mechanisms are not known with certainty.

Age-Related Eye Diseases

Cataracts

Cataracts are thought to be caused by oxidative damage of proteins in the eyes lens induced bylong-term exposure to UV light. The resulting cloudiness and discoloration of the lens leads tovision loss that becomes more severe with age. The results of several large prospective cohortstudies suggest that diets rich in fruits and vegetables, especially carotenoid and vitamin C-richfruits and vegetables, are associated with decreased incidence and severity of cataracts (57-60). Ina study of male U.S. health professionals, high intakes of both broccoli and spinach wereassociated with fewer cataract extractions (57).

Macular Degeneration

Degeneration of the macula, the center of the retina, is the leading cause of blindness in peopleover the age of 65 in the United States (61). Lutein and zeaxanthin are carotenoids that are foundin relatively high concentrations in the retina; these carotenoids may play a role in preventingdamage to the retina caused by light or oxidants (62). In two case-control studies, high intakes ofcarotenoid-rich vegetables, especially those rich in lutein and zeaxanthin, such as dark green, leafyvegetables, were associated with a significantly lower risk of developing age-related maculardegeneration (AMD) (63, 64). In a prospective cohort study of more than 118,000 men andwomen, those who consumed three or more servings of fruits daily had a risk of developing age-related macular degeneration over the next 12-18 years that was 36% lower than those whoconsumed less than 1.5 servings (65). Interestingly, vegetable intake was not associated with therisk of macular degeneration in this cohort. In a more recent study, combined lutein andzeaxanthin intake was not associated with prevalence of intermediate AMD in a cohort of womenaged 50-79 years (66). However, further analysis of the data revealed that women younger than75 years with stable intakes of lutein and zeaxanthin had a 43% lower risk of developingintermediate AMD (66).

Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a term that includes emphysema and chronicbronchitis, two chronic lung diseases that are characterized by airway obstruction. Althoughsmoking is by far the most important risk factor for COPD, the results of several epidemiologicalstudies suggest beneficial associations between vegetable and, more strongly, with fruit intakesand COPD risk (67). The results of several epidemiological studies in Europe indicate that higher

fruit intakes, especially apple intakes, are associated with higher forced expiratory volume (FEV1)values, indicative of better lung function (68-70). In a study of 2,500 middle-aged Welsh men,those who ate at least five apples weekly had significantly slower declines in lung function thanthose who did not eat apples over a 5-year period (69). In a study of 2,917 European men followedover 20 years, each 100 g (3.5 oz) increase in daily fruit consumption was associated with a 24%decrease in the risk of death from COPD (71). The reasons for the beneficial association betweenfruit intake and lung health are not yet known. Because oxidative stress is thought to play a role inthe etiology of chronic obstructive lung disease, scientists are currently investigating the possibilitythat antioxidants found in fruits, such as vitamin C or flavonoids, could play a protective role.Higher fruit and vegetable intake was inversely associated with risk of COPD in a small case-controlstudy of male cigarette smokers (72), providing support for the antioxidant hypothesis.




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Interestingly, when compared to a Western dietary pattern (refined grains, cured and red meats,French fries, and desserts), a prudent dietary pattern that emphasized fruits, vegetables, fish, andwhole grains was associated with a 25-50% reduction in COPD risk in large cohorts of men (73)and women (74).

Neurodegenerative Disease

Although it is not yet clear whether a diet rich in fruits and vegetables will decrease the risk ofneurodegenerative diseases like Alzheimers disease and Parkinsons disease in humans, recentstudies in animal models of these diseases suggest that diets rich in fruits like blueberries (75) ortomatoes may be protective (76). Interestingly, a prospective study that followed 1,836 olderJapanese Americans for an average of 6.3 years found that regular consumption of fruit andvegetable juices was associated with a decreased risk of developing Alzheimer's disease (77). Morestudies are needed to determine whether fruit and vegetable consumption is protective againstneurodegenerative diseases.

Intake Recommendations

Many agencies within the U.S. government, including the Centers for Disease Control andPrevention, recommend eating a variety of fruits and vegetables daily; the recommended serving

number depends on age, sex, and activity level (78). The table below provides some examples of asingle serving of fruits or vegetables. The 2005 Dietary Guidelines for Americans are similar withrespect to fruit and vegetable intake recommendations, but they are tied to caloric intake and notto age or gender (79). Daily consumption of 2 cups (4 servings) of fruit and 2 cups (5 servings)of vegetables are recommended for people who consume 2,000 kcal/d, while 1.5 cups of fruit and(3 servings) and 2 cups (4 servings) of vegetables are recommended for people who consume1,600 kcal/d. In both cases, consumption of a variety of different fruits and vegetables isrecommended, including dark green, red, orange, yellow, blue, and purple fruits and vegetables, aswell as legumes (peas and beans), onions, and garlic. The Linus Pauling Institute's Prescription forHealth states that potatoes should not be included in the daily tally of fruit and vegetable intake.Moreover, certain groups of fruits and vegetables, such as cruciferous vegetables, may providespecific health benefits (see the article on Cruciferous Vegetables). Additionally, fiber-rich, wholefruits are recommended over high-sugar fruit juices.

Examples of One Serving of Fruits or Vegetables

6 fluid ounces of fruit or vegetable juice ( of a cup)

1 medium sized apple or orange

1 small banana

1 cup of raw salad greens

cup of cooked vegetables (about the size of a baseball)

cup of chopped fruit or vegetables

cup of cooked peas or beans

cup of dried fruit (about the size of a golf ball)

Some Potentially Beneficial Compounds in Fruits and Vegetables

Vitamins Minerals Phytochemicals

Folate Magnesium Carotenoids

Vitamin A Potassium Chlorophylls

Vitamin C Selenium Fiber




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Vitamin E Flavonoids

Vitamin K Indole-3-Carbinol

Isoflavones

Isothiocyanates

Lignans

Phytosterols

References

Written in December 2005 by:Jane Higdon, Ph.D.

Linus Pauling InstituteOregon State University

Updated in May 2009 by:Victoria J. Drake, Ph.D.

Linus Pauling InstituteOregon State University

Reviewed in May 2009 by:Kaumudi Joshipura, Sc.D.Professor of Epidemiology

Harvard School of Public HealthAssociate Professor

Harvard School of Dental Medicine

Last updated 4/7/2010 Copyright 2003-2012 Linus Pauling Institute

Disclaimer

The Linus Pauling Institute Micronutrient Information Center provides scientific information onhealth aspects of micronutrients and phytochemicals for the general public. The information ismade available with the understanding that the author and publisher are not providing medical,psychological, or nutritional counseling services on this site. The information should not be used inplace of a consultation with a competent health care or nutrition professional.

The information on micronutrients and phytochemicals contained on this Web site does not coverall possible uses, actions, precautions, side effects, and interactions. It is not intended as medicaladvice for individual problems. Liability for individual actions or omissions based upon the contentsof this site is expressly disclaimed.


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