Fish is rich in the long-chain polyunsaturated omega-3 fatty acids, eicosapentanoic
acid (EPA) and docosahexonoic acid (DHA) and low in saturated fatty acids. The
American Heart Association recommends eating one serving (3.5 oz. cooked, or
about ¾ cup of flaked fish) of a variety of fish at least twice a week. Omega-3 fatty
acids from fish are associated with decreased risk of abnormal heartbeats (arrhythmias),
which can cause sudden death, decreased triglyceride levels, and decreased risk of diabetic retinopathy and atherosclerotic plaque. A meta-analysis of 19 different studies found that consumption of fish was associated
with about a 20% decrease in unstable angina and heart attack among those who ate
the most fish, four times per week. An earlier blog noted that omega-3 fish oil supplements do not seem to provide
that same benefits that fish do.
The omega-3 content of fish varies according to their species and whether they are
farmed or not. Fatty fish like salmon, mackerel, herring, lake trout, sardines, and
albacore tuna are high in omega-3 fatty acids. Other fish are lower in omega-3 content.
For example, tilapia has about 0.2 grams of omega-3s per serving compared to
wild or farmed salmon with more than 1.5 grams.
Fish is not risk-free. Some types of fish may contain high levels of mercury, mostly
in the form of methylmercury, PCBs (polychlorinated biphenyls), dioxins and other
environmental contaminants. Levels of these substances are generally highest in
animals at the top of the food chain that are older, larger, and in predatory fish.
Mercury is of concern, especially for children and pregnant women, because of the
potential for adverse effects on fetal and child neurodevelopment and adult cardiovascular
disease. Children and pregnant women are advised by the FDA to avoid
eating fish with the potential for the highest level of mercury contamination (e.g.,
shark, swordfish, king mackerel or tilefish); and to only eat up to 12 ounces (two
average meals) per week of a variety of fish and shellfish that are lower in mercury.
Low mercury seafood includes shrimp, scallops, sardines, salmon, oysters, tilapia
canned light tuna, pollock, and catfish.
An increasing share of fish sold in the U.S. is farmed and imported. These sources
also entail risks to health. Aquaculture feeds fish with an unnatural diet that may
include high levels of pesticides, antibiotics, and other toxins. China supplies almost
60% of the $90 billion global aquaculture trade, and contamination of Chinese
seafood with antibiotics is not uncommon. Foreign countries provide 90% of the
shrimp consumed in the U.S., and that too is sometimes rejected by the FDA because
of antibiotic contamination. Fish farmed in Canada and European countries
have a better safety record than those from Asian and Latin American countries that
have less rigorous standards for the avoidance of contamination and for minimizing
the environmental impact of their farming methods.
There are a variety of guides to assist consumers in buying seafood that is both
healthy and responsibly farmed or wild-caught. The Environmental Defense Fund
(EDF) has a Seafood Selector that is available at http://seafood.edf.org/guide/best
The Monterey Bay Seafood Watch website at https://www.seafoodwatch.org provides
U.S. state-specific guides to sustainable seafood.
Eating fish and other kinds of seafood can be healthy, but making choices that are
safe and ecologically responsible requires careful selection. It may be just as beneficial
to health to substitute plant-based foods, vegetables, fruit, beans, and nuts for
red meat and processed meats as it is to substitute seafood. There is just not enough
wild or farmed seafood for all 7.8 billion of us on the planet to eat seafood twice a
This blog presents opinions and ideas and is intended to provide helpful general information. I am not engaged in rendering advice or services to the individual reader. The ideas, procedures and suggestions in that are presented are not in any way a substitute for the advice and care of the reader’s own physician or other medical professional based on the reader’s own individual conditions, symptoms or concerns. If the reader needs personal medical, health, dietary, exercise or other assistance or advice the reader should consult a physician and/or other qualified health professionals. The author specifically disclaims all responsibility for any injury, damage or loss that the reader may incur as a direct or indirect consequence of following any directions or suggestions given in this blog or participating in any programs described in this blog or in the book, The Building Blocks of Health––How to Optimize Your Health with a Lifestyle Checklist (available in print or downloaded at Amazon, Apple, Barnes and Noble and elsewhere). Copyright 2021 by J. Joseph Speidel.