Should We Tell People to
Eat Fish?Joyce A. NettletonScience Communications
ConsultantEditor, PUFA Newsletter
Denver, CO
Rutgers Cooperative ExtensionJune 8, 2004
Should We Eat Fish?
Heart Health Neurodevelopment
Mental Health
Gene Expression
Immune &Inflammatory
Function Respiratory Function
VisualFunction
ClinicalConditions
Should We Eat Fish?
When Biotechnology Breakthroughs Focus on
Omega-3s . . .
Transgenic canola produced 16% to 23% stearidonic acid (18:4n-3), Calgene,1999
Transgenic mice converted omega-6 to omega-3 PUFAs, Feb. 2004
Transgenic Arabidopsis thaliana synthesized EPA and AA, May 2004
Should We Eat Fish?
Should We Tell People to Eat Fish?
Should We Eat Fish?
When the American Heart Association . . .
“Recommends that all adults eat fish (particularly fatty fish) at least two times a week” . . .
Should We Eat Fish?
WhenInstitute of MedicineThe World Health OrganizationDietary Guidelines for AmericansNHLBI and NCEPCountries around the world
All recommend increased fish consumption . . .
Should We Eat Fish?
Should We Tell People to Eat
Fish?
Should We Eat Fish?
Should We Eat Fish?
Instead of the Good News . . .
Mercury Policy Project PCRM EPA Anti Aquaculture Groups Environmental Working Group Authors of the Hites study, Jan/04
California Prop 65
Should We Eat Fish?
Each of these groups has an agenda unrelated to health . . .
Eliminate Hg emissions Clean up or abolish aquaculture Increase political turf Promote environmental agenda Increase regulation
Should We Eat Fish?
No Argument About . . . Toxicity of methylmercury and risks in fetal
development
Presence of Hg and other contaminants in fish and shellfish
Some species more contaminated than others
Higher levels in larger older fish than in younger smaller fish
Should We Eat Fish?
But we have forgotten . . .
Should We Eat Fish?
“It’s the dose that makes the poison”
- Paracelsus 1493-1541
Should We Eat Fish?
Methylmercury Damages fetal neurodevelopment
Concentrates up food chain with size and age of fish
Present throughout fish tissues
Some protection from damage by vitamin E and selenium
Gradually eliminated t50= 50-70 days in adults, 90 in children
Should We Eat Fish?
Methylmercury
Majority of Americans are at low risk of adverse health effects from methylmercury: EPA
EPA reference dose: 0.1 μg MeHg/kg body wt/day – 7 μg/day
FDA: 1 ppm max in fish
Canada: 0.5 ppm max in fish
Should We Eat Fish?
To Minimize Risk Avoid shark, swordfish, king mackerel,
tilefish, some sport fish Choose species low in Hg- salmon, trout,
sardines, mackerel, herring, light tuna, troll-caught tuna, tilapia, flatfish, shellfish
Eat a variety of species Heed consumption advisories
Should We Eat Fish?
Organic contaminants PCBs – Environmental levels since
mid 1980s; fish levels FDA limit: 2000 ppb
EPA: combined estimated risks for several substances assuming risks are additive; includes more substances than FDA
Should We Eat Fish?
Organic contaminants
FDA: 2000 ppb Hites study: Wild salmon 5 ppb Farmed salmon, 37 ppb
WHO: Toxic equivalents: 1-4 pcg/kg body wt/day
Hites study: 0.48 - 2.7 pcg/kg/bw/day
Should We Eat Fish?
Farmed vs.Wild Different species: Atlantic vs five Pacific
species Higher fat content: 10.9 vs 4.4-7.5 g/100g Sockeye & king: 10.9-13.3 g/100g More EPA+DHA: 2.4 vs 1.0-1.7 Both low in Hg and other contaminants Issues pertain to environmental not safety Added castaxanthin or astaxanthin are same
as naturally occurring colorants
Should We Eat Fish?
Should We Tell People to Eat
Fish?
Should We Eat Fish?
Cardiovascular Benefits
Reduce the chance of sudden death by making arrhythmia less likely
> 300,000 deaths/yr are “sudden deaths”
> 80% of these are sudden cardiac deaths – preventable ones
Should We Eat Fish?
GISSI Study – 11,324 MI survivors who consumed 850-880 mg EPA+DHA/day had:
45% in sudden death after 4 mo. 30% cardiovascular death 20% death from all causes after 3 mo.
Many other studies have reported mortality from sudden death with fish or EPA+DHA consumption, mostly in patients with CVD or type 2 diabetes
Should We Eat Fish?
Reduce the risk of total CVD mortality Many epidemiological studies have reported
mortality of 20% to 40% or more in populations consuming fish regularly
Protection often but not always dose related, with consumption of 1-2 fish meals/wk providing maximum protection
Should We Eat Fish?
Reduce the risk of having a first MI Prevalence of MI in elderly Dutch who
consumed fish
Risk of CHD in Japanese-American men in Hawaii who smoked, but ate fish
Risk of CHD in women who ate fish
Risk of first MI in Swedish men & women
Not all studies have observed of MI or heart disease with fish consumption
Should We Eat Fish?
Reduce the risk of stroke Risk of ischemic stroke by 45% in men 40-75
yr who ate fish 1-3 x a month
Risk of all stroke in middle aged women, with risk inversely related to amount consumed
Moderate fish or n-3 LC-PUFA consumption, up to 3 g/day, does not risk of hemorrhagic stroke
Very high intake (>10 g/day) of n-3 LC-PUFAs associated with risk of hemorrhagic stroke
Should We Eat Fish?
Reduce severity of atherosclerosis Recent evidence that fish oils may stabilize
atherosclerotic plaques making them less likely to rupture
Fish oil consumption for 2 yr related to artery diameter
Modest improvement in restenosis in some but not all studies
Should We Eat Fish?
Improve vascular function Inhibit excess reactivity in cells lining the blood
vessels reducing inflammatory responses
Promote vascular relaxation which improves blood flow and reduces blood pressure
Should We Eat Fish?
Reduce inflammation Inflammation now recognized as an important
risk factor in CVD and is in CVD, type 2 diabetes, metabolic syndrome, hypertension, microalbuminuria
n-3 LC-PUFAs inflammatory markers and mediators of inflammatory responses (cytokines)
Should We Eat Fish?
Improve blood lipids Reduce triglycerides especially in people with
high levels, e.g., those with type 2 diabetes, other dyslipidemias
Improve HDL levels, especially in people with CVD, type 2 diabetes
Modest in LDL that occurs in some people outweighed by TGs and HDL and other CV benefits
Should We Eat Fish?
Reduce risk of blood clotting Risk of platelet aggregation
May some clotting factors such as fibrinogen
May clot breakdown
Should We Eat Fish?
Modestly reduce blood pressure Consumption of fish oil or EPA+DHA is
associated with modest reductions in systolic and diastolic blood pressure, especially in those with elevated pressure
Should We Eat Fish?
Boost the effectiveness of “statins” n-3 LC-PUFAs increase the effectiveness of
statin drugs prescribed to lower LDL cholesterol levels
LDL levels are further
HDL levels are further
Should We Eat Fish?
Reduce the risk of type 2 diabetes Type 2 diabetics have 3x risk of CVD
Regular consumption of fish or n-3 LC-PUFAs reduces the risk of developing type 2 diabetes in those who are insulin resistant or at high risk
n-3 LC-PUFAs improve blood lipids, vascular function, reduce inflammation
n-3 LC-PUFAs risk of CVD in those with type 2 diabetes
Should We Eat Fish?
Should We Tell People to Eat
Fish?
Should We Eat Fish?
Other Health Effects Essential for fetal & infant neuro-
development – very important to consume n-3 LC-PUFAs during pregnancy & lactation
Modulate immune & inflammatory function – rheumatoid arthritis, asthma, psoriasis, atopy
May risk of some cancers May risk of age-related macular
degeneration
Should We Eat Fish?
Other Health Effects May risk of certain mental disorders, e.g.
depression, bipolar disorder, Alzheimer’s
May symptoms of cystic fibrosis
May improve graft patency in dialysis
May improve symptoms of atopy
Should We Eat Fish?
Should We Tell People to Eat Fish?
Should We Eat Fish?
Not All Omega-3s Are Equal Fish have long-chain omega-3s, EPA & DHA Plants have alpha-linolenic acid, 18:3n-3, which
is converted to long-chain forms inefficiently (<1%)
Conversion of ALA is inhibited by n-6 and n-3 PUFAs
High levels of ALA do not conversion ALA has been associated with risk of CVD
and risk of prostate cancer – this issue needs to be resolved
Should We Eat Fish?
Should We Tell People to Eat
Fish?
Should We Eat Fish?
Current Treatment for CVD
Should We Eat Fish?
Inuit Approach . . .