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Adverse Effects of Omega-3 Fatty Acid Intake
There are few recognized adverse effects of omega-3 fatty
acid administration. When present, they are related almost exclusively to the
administration of supplements in capsule or pill form.
Subjects reported a higher incidence of
both belching and unpleasant taste if they were taking fish oil capsules rather
than olive oil capsules, or some other placebo. This adverse effect seems
entirely limited to those using supplements, such as the fish oil capsules, to
ingest omega-3 FAs. People who increase their omega-3 FA intake purely by
dietary means (eating more fish, flaxseed, flaxseed oil, etc.) have experienced
no adverse effects.
Omega-3 fatty acids exert a dose-related effect on bleeding
time; however, there are no documented cases of abnormal bleeding as a result of
fish oil supplementation, even at high dosages and in combination with other
anticoagulant medications.
However, Omega-3 fatty
acids should be used cautiously by people who bruise easily, have a bleeding
disorder, or take blood-thinning medications. Intake should be
limited to less than three grams per day (less than 3 servings of fish per day).
High dosages of fish oil may increase LDL cholesterol
levels, but the clinical relevance of this finding remains unclear.
Although past
studies have found that regular consumption of fish may reduce the risk of
macular degeneration, a recent study found that diets rich in ALA may actually
increase the risk of this disease. Until more data is obtained, it is best
for people with macular degeneration to obtain omega-3 fatty acids from sources
of EPA and DHA, rather than ALA.
No adverse effects on pregnancy have been shown in humans.
Some studies in animals have reported an increase in the rates of prolonged and
difficult labors and an increase in blood loss during labor. These results were
shown only with much higher doses of omega-3 FA than have ever been used in
human studies. These effects have not been shown in human studies.
It is important to be aware of the
two types of fish oil supplement — those made from the
liver of the fish and those made from the body of the fish. Supplements made
from the liver of the fish, such as cod liver oil, contain the retinol form of
vitamin A and need to be either avoided altogether or strictly limited in
pregnancy so that your daily intake does not exceed 3,300 micrograms (mcg). On
the other hand, fish oils not derived from fish livers contain lots of
DHA (docosahexaenoic acid), which is essential for your baby's developing eyes
and brain.
Significant amounts of methylmercury, polychlorinated
biphenyls, dioxins, and other environmental contaminants may be concentrated in
certain species of fish, such as shark, swordfish, king mackerel, and tilefish
(also known as golden bass or golden snapper).
In March 2004, the U.S. Food and Drug Administration (FDA) and the
Environmental Protection Agency issued a new statement
advising women who may become pregnant, women who are pregnant, breastfeeding
mothers, and young children to avoid eating some types of fish and to eat fish
and shellfish that are lower in mercury. These recommendations can be found by
visiting: http://www.cfsan.fda.gov/~dms/admehg3.html.
High-quality fish oil supplements usually do not contain these contaminants.
Although it has not been shown to be statistically
significant in human studies, there is a theoretical risk of increasing the rate
of post-term delivery when increasing omega-3 FA intake throughout pregnancy.
If the use of omega-3 FAs during an entire pregnancy or during the third
trimester results in longer duration of pregnancy, then it makes intuitive sense
that pregnancies that would have culminated with labor at 40 weeks gestation without the increase in omega-3 FA might be prolonged as well, resulting in an
increase in the rate of post-term (>42 weeks gestation) deliveries. Combating
this theoretical risk would be easily accomplished by having women stop their
method of omega-3 supplementation around 38 weeks gestation. As stated
previously, though, this has only been shown as a trend in recent research, not
as a statistically significant adverse effect. The risk is theoretical.
Because of
the potential for side effects and interactions with medications, dietary
supplements should be taken only under the supervision of a knowledgeable
healthcare provider.
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