Should We Tell People to
Eat Fish?
Joyce A. Nettleton
Science Communications Consultant
Editor, PUFA Newsletter
Denver, CO
Rutgers Cooperative Extension
June 8, 2004
Should We Eat Fish?
Heart Health
Neurodevelopment
Mental Health
Gene Expression
Immune &
Inflammatory
Function
Respiratory
Function
Visual
Function
Clinical
Conditions
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?
When
Institute of Medicine
The World Health Organization
Dietary Guidelines for Americans
NHLBI and NCEP
Countries 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 . . .
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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
Farmed vs.Wild
Should We Eat Fish?
 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?
Other Health Effects
Should We Eat Fish?
 Essential for fetal & infant neurodevelopment – 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 . . .