Febrary 21, 2005
You may have heard about
the health benefits of omega-3 fatty acids.
"Omega-3 fatty acids
benefit the heart of healthy people, and those at high risk of
-- or who have -- cardiovascular disease. We [the American Heart
Association] 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). ... 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."
While omega-3 fatty acids
come from many sources, fish seem to get the most attention --
and the most press.
"Press Release Date:
April 22, 2004
Fish oil can help reduce deaths from heart disease, according
to new evidence reports announced today by the Agency for Healthcare
Research and Quality [AHRQ]. The
systematic reviews of the available literature found evidence
that long chain omega-3 fatty acids, the beneficial component
ingested by eating fish or taking a fish oil supplement, reduce
heart attack and other problems related to heart and blood vessel
disease in persons who already have these conditions, as well
as their overall
risk of death. ... The review also found other evidence indicating
that fish oil can help lower high blood pressure slightly, may
reduce risk of coronary artery re-blockage
after angioplasty, may increase exercise capability among patients
with clogged arteries, and may possibly reduce the risk of irregular
heart beats -- particularly in
individuals with a recent heart attack. 'These findings will help
health care professionals and the public understand which benefits
of omega-3 fatty acids have been scientifically proven and pinpoint
areas where additional evidence is needed,' said Carolyn M. Clancy,
M.D., AHRQ's Director."
With all of the recommendations
and positive attention that fish and omega-3 fatty acids have
been receiving, one might get the impression that adding some
omega-3s will cure all ailments.
"The quantity and
strength of evidence for effects of omega-3 fatty acids on outcomes
in the conditions assessed varies greatly. The findings of many
studies among type II diabetics provide strong evidence that omega-3
fatty acids reduce serum triglycerides but have no effect on total
cholesterol, HDL cholesterol, and LDL cholesterol. For rheumatoid
arthritis, the available evidence suggests that omega-3 fatty
acids reduce tender joint counts and may reduce requirements for
corticosteroids, but does not support an effect of omega-3 fatty
acids on other clinical outcomes. There are insufficient data
available to draw conclusions about the effects of omega-3 fatty
acids on inflammatory bowel disease, renal disease, SLE, bone
density, or fractures or the effects of omega-3 fatty acids on
insulin resistance among type II diabetics."
While omega-3 fatty acids
do have important health benefits, getting them all from fish
may have some risks.
"Last year the Food
and Drug Administration determined there is so much mercury in
the sea that women of childbearing age should severely limit their
consumption of larger ocean fish. ... In adults, mercury poisoning
can cause numbness, stumbling, dementia, and death. 'It's no secret
that mercury exposure is highly toxic,' says toxicologist Alan
Stern, a contributor to a 2000 National Research Council report
on mercury toxicity. ... Data now suggest effects might occur
at levels lower than anyone suspected. Some studies show that
children who were exposed to tiny amounts of mercury in utero
have slower reflexes, language deficits, and shortened attention
spans. In adults, recent studies show a possible link between
heart disease and mercury ingested from eating fish."
Mercury is bad, but this
does not mean that fish should be removed from everyone's diet.
"There are plenty
of good reasons to eat fish: It's high in protein, low in unhealthy
fat, and rich in healthful omega-3s. But recent reports have questioned
the safety of eating fish, due to potentially unacceptable levels
of PCBs and mercury. PCBs (polychlorinated biphenyls) and mercury
are industrial pollutants that find their way into fresh waters
and oceans where they are absorbed by fish. ... PCBs have been
linked to a variety of health problems, but there is no official
agreement that the amount of PCBs in farmed fish poses a health
hazard. ... As for mercury, high levels may damage the developing
nervous system. ... Adding plant foods that contain omega-3s to
a diet that only has limited amounts of fatty fish is advantageous.
Plant sources contain a shorter-chain fatty acid, called ALA (alpha-linolenic
acid), that humans can convert to the type of omega-3s fish has,
but it is not as effective as obtaining omega-3s from fish."
With all that said, how
can you know what is right for you.The recommendations are different
for different groups. In general, guidelines suggest:
"* Continue eating a variety of fish, but limit your consumption
of farmed salmon to two 3 oz. servings per week. Wild salmon is
usually available frozen or canned.
* To reduce PCBs, remove skin and visible fat from fish. Bake,
broil or grill fish instead of frying.
* Add plant foods that contain omega-3s."
If you are concerned
about eating too much fish, you can always,
"Add plant foods
that contain omega-3s," but what if you are a vegetarian,
and you don't eat fish at all? What sources of omega-3s are available
* Flaxseed and flaxseed oil
* Canola oil
* Wheat germ
* Green leafy vegetables (including spinach, kale, leeks and broccoli)
* Dried beans (such as kidney, garbanzo and pinto)"
Questions of the Week:
Why are omega-3 fatty acids an important part of a healthy diet?
How are different sources better (or worse) for different people?
How can you know what sources (and what quantities of those sources)
are right for you? If you do eat fish, how can you balance the
possible health benefits and the possible health risks? Which
types of fish should you choose over others? Which should you
avoid entirely? If you do not eat fish, what can you do to get
the right amount of omega-3s for your body? Whether or not you
eat fish, how can you balance a variety of sources in order to
maximize the health benefits of the omega-3s your body is getting
-- while, at the same time, minimize the risks and health hazards
associated with some sources?