Fish offers our
best dietary source of omega-3 fat, the type of fat identified as protective
against heart disease, dementia, inflammation and potentially cancer. But with
several different types of omega-3s and varying amounts in different varieties
of fish and other foods, consumers are often confused about how best to
maximize their dietary intake.
includes both ALA, which is found in plant foods such as flax, walnuts and
canola oil, and EPA and DHA, found only in seafood and algae. Health experts
used to consider all three together when evaluating the benefits of omega-3
fats, but evidence increasingly shows that humans are relatively inefficient at
converting ALA into EPA and DHA.
most Americans do not eat enough fish to obtain the levels of EPA and DHA
identified as protective.
consumption averages about 2.5 to 3 ounces a day in the U.S., much of which
includes fish that is relatively low in omega-3 fat like shrimp, pollock,
tilapia and catfish. To meet current recommendations, Americans are encouraged
to choose fish that are naturally high in fat: examples include salmon,
mackerel, trout, sardines and albacore (white) tuna.
The good news: A
mere 8 ounces of fatty/oily fish per week is all that is needed to reach the
recommended amount of omega-3s for preventive heart health benefits (500
milligrams of EPA and DHA per day).
People who already have heart disease should try to average 1000 mg per
day, consuming about 16 ounces of fatty fish per week. Those with elevated
blood triglycerides may benefit from 2000 to 4000 mg a day, but this will
almost always require supplements and should be taken under a physician’s care.
EPA and DHA-specific recommendations, questions arise about whether vegetarians
and others who don’t eat fish can get equal health benefits from high intake of
ALA. Several studies link higher ALA consumption with lower heart disease, but
it’s not clear whether nonfish-eaters are protected through dietary sources
like flaxseed oil and walnuts alone, or if using EPA and DHA-fortified foods or
algal supplements provides further protection.
protective effects of omega-3 fats seem to come by increasing body production
of anti-inflammatory hormone-like compounds called eicosanoids.
But this benefit may be diminished if other
polyunsaturated fats – omega-6 fats – are eaten in excess. These fats (found in
corn and safflower oil and fish like farmed tilapia and catfish) boost production
of different eicosanoids that
While some research
focuses on finding an ideal dietary ratio between the two fats, this approach
is hotly debated.
Rather, many experts
recommend that we simply focus our attention on increasing the amount of
omega-3 sources in our diet. The best advice to meet this goal: Eat at least
two servings of high omega-3 fish (oily fish) per week.
research is giving us a clearer picture of how omega-3 fat protects our hearts;
promoting normal blood pressure, heart rhythm and blood clotting seem to be its
Studies also show
that omega-3 fat, in utero and during infancy, clearly benefit babies’ visual
and nervous system development. Experts are trying to encourage women of
childbearing age to consume 8 to 12 ounces of seafood weekly, simply avoiding
those fish highest in mercury.
researchers are starting to look at a potential link between omega-3
consumption and cancer protection. While a major report on diet and cancer risk
did not find any concrete evidence, it did note that some emerging (though
limited) research suggests a link between fish consumption and lower risk of
colon cancer. Additional laboratory studies suggest that omega-3’s
anti-inflammatory effects could reduce cancer development, but studies are not
consistent. If a link does exist, it is possible that the benefit of omega-3
fish is being obscured by studies that look at total fish consumption, grouping
fish high in omega-3 fat together with low fat fish and batter-covered fish
high in omega-6 fat.
September 29, 2008
Contact: Sarah Wally, (202) 328-7744
The American Institute for Cancer Research
(AICR) is the cancer charity that fosters research on the relationship of
nutrition, physical activity and weight management to cancer risk, interprets
the scientific literature and educates the public about the results. It has
contributed more than $86 million for innovative research conducted at
universities, hospitals and research centers across the country. AICR has
published two landmark reports that interpret the accumulated research in the
field and is committed to a process of continuous review. AICR also provides a
wide range of educational programs to help millions of Americans learn to make
dietary changes for lower cancer risk. Its award-winning New American Plate
program is presented in brochures, seminars and on its Web site, www.aicr.org.
AICR is a member of the World Cancer Research Fund International.
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