Fish Oil and Mercury

BOSTON, MASSACHUSETTS. The benefits of eating fish are related to the content of the long-chain omega-3 fatty acids EPA and DHA. The risk is associated with a whole host of contaminants such as mercury, PCBs etc. Thus the question—do the benefits outweigh the risks? A detailed examination of this question appeared in the October 18th issue of the Journal of the American Medical Association. Mozaffarian and Rimm from Harvard Medical School first review the cardiovascular and neurological developmental benefits of fish and in particular the fatty acids EPA and DHA for which fish provide a significant dietary source. Numerous studies relating to the cardiovascular benefits of EPA and DHA are presented in tables and impressive graphs. DHA is also critical in the neurological development during gestation and the first 2 years of infancy. A number of studies are quoted to support the importance of maternal intake of DHA during pregnancy and while nursing. The other aspect of the question, i.e. the risks associated with contaminants, is much more difficult to address. Medical scientists obviously do not conduct experiments on humans where the dose dependence of toxicity from the contaminants in question is investigated by giving the participants toxic chemicals and observing the results. Thus data for high doses must come from accidental or occupational exposure but these levels are irrelevant in terms of the levels found in most fish. At the other end of the dose spectrum, making an association between the intake of traces of toxic materials and adverse health outcomes is very difficult and fraught with uncertainty and confounding.

Read more: Fish intake—Risks and benefits

BALTIMORE, MARYLAND. Several studies have shown that regular fish consumption protects against cardiovascular disease. Other studies have shown that consuming mercury-contaminated fish increases the risk of coronary heart disease. The beneficial effect of fish consumption is believed to be due to the presence of the omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the tissue of fish and shellfish. Two recent studies have attempted to answer the question "Are the beneficial effects of fish oils (EPA and DHA) outweighed by the negative effects of mercury"?

Read more: Fish, mercury, and heart disease

Fish Intake and Omega 3 & 6

MONTREAL, CANADA. The American Heart Association and similar organizations have long extolled the virtue of consuming fish once or preferably twice a week as a powerful preventive measure against cardiovascular disease. Although there is increasing evidence that most fish now contain mercury (especially methylmercury), it is still felt that regular fish consumption is beneficial overall.

University of Quebec researchers now question the assumption that fish consumption is universally beneficial. They do not question whether an increased intake of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is beneficial; however, they do question whether all fish actually ends up contributing to the body’s stores of DHA and EPA when consumed.

Read more: Health benefits of saltwater fish vs freshwater fish