Fish and Omega-3 Fatty Acids
http://www.americanheart.org/presenter.jhtml?identifier=4632
AHA Recommendation
Omega-3 fatty acids benefit the heart of healthy people, and those at
high risk of — or who have — cardiovascular disease.
We recommend eating fish (particularly fatty fish) at least two times
a week. Fish is a good source of protein and doesn’t have the
high saturated fat that fatty meat products do. Fatty fish like mackerel,
lake trout, herring, sardines, albacore tuna and salmon are high in
two kinds of omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic
acid (DHA).
To learn about omega-3 levels for different types of fish — as
well as mercury levels, which can be a concern — see our Encyclopedia
entry on Fish, Levels of Mercury and Omega-3 Fatty Acids.
We also recommend eating tofu and other forms of soybeans, canola, walnut
and flaxseed, and their oils. These contain alpha-linolenic acid (LNA),
which can become omega-3 fatty acid in the body. The extent of this
modification is modest and controversial, however. More studies are
needed to show a cause-and-effect relationship between alpha-linolenic
acid and heart disease.
The table below is a good guide to use for consuming omega-3 fatty acids.
Summary of Recommendations for Omega-3 Fatty Acid Intake
Population Recommendation
Patients without documented coronary heart disease (CHD) Eat a variety
of (preferably fatty) fish at least twice a week. Include oils and foods
rich in alpha-linolenic acid (flaxseed, canola and soybean oils; flaxseed
and walnuts).
Patients with documented CHD Consume about 1 g of EPA+DHA per day,
preferably from fatty fish. EPA+DHA supplements could be considered
in consultation with the physician.
Patients who need to lower triglycerides 2 to 4 grams of EPA+DHA per
day provided as capsules under a physician’s care.
Patients taking more than 3 grams of omega-3 fatty acids from supplements
should do so only under a physician’s care. High intakes could
cause excessive bleeding in some people.
Background
In 1996 the American Heart Association released its Science Advisory,
“Fish Consumption, Fish Oil, Lipids and Coronary Heart Disease.”
Since then important new findings have been reported about the benefits
of omega-3 fatty acids on cardiovascular disease. These include evidence
from randomized, controlled clinical trials. New information has emerged
about how omega-3 fatty acids affect heart function (including antiarrhythmic
effects), hemodynamics (cardiac mechanics) and arterial endothelial
function. These findings are outlined in our November 2002 Scientific
Statement, “Fish Consumption, Fish Oil, Omega-3 Fatty Acids and
Cardiovascular Disease.”
The ways that omega-3 fatty acids reduce CVD risk are still being studied.
However, research has shown that they
decrease risk of arrhythmias, which can lead to sudden cardiac death
decrease triglyceride levels
decrease growth rate of atherosclerotic plaque
lower blood pressure (slightly)
What do epidemiological and observational studies show?
Epidemiologic and clinical trials have shown that omega-3 fatty acids
reduce CVD incidence. Large-scale epidemiologic studies suggest that
people at risk for coronary heart disease benefit from consuming omega-3
fatty acids from plants and marine sources.
The ideal amount to take isn’t clear. Evidence from prospective
secondary prevention studies suggests that taking EPA+DHA ranging from
0.5 to 1.8 grams per day (either as fatty fish or supplements) significantly
reduces deaths from heart disease and all causes. For alpha-linolenic
acid, a total intake of 1.5–3 grams per day seems beneficial.
These data support the 2000 AHA Dietary Guidelines recommendation to
include at least two servings of fish (particularly fatty fish) per
week.
Randomized clinical trials have shown that omega-3 fatty acid supplements
can reduce cardiovascular events (death, non-fatal heart attacks, non-fatal
strokes). They can also slow the progression of atherosclerosis in coronary
patients. However, more studies are needed to confirm and further define
the health benefits of omega-3 fatty acid supplements for preventing
a first or subsequent cardiovascular event. For example, placebo-controlled,
double-blind, randomized clinical trials are needed to document the
safety and efficacy of omega-3 fatty acid supplements in high-risk patients
(those with type 2 diabetes, dyslipidemia, hypertension and smokers)
and coronary patients on drug therapy. Mechanistic studies on their
apparent effects on sudden death also are needed.
Increasing omega-3 fatty acid intake through foods is preferable. However,
coronary artery disease patients may not be able to get enough omega-3
by diet alone. These people may want to talk to their doctor about taking
a supplement. Supplements also could help people with high triglycerides,
who need even larger doses. The availability of high-quality omega-3
fatty acid supplements, free of contaminants, is an important prerequisite
to their use.