A new report by the Institute of Medicine (IOM) at the National Academy of Sciences affirms that eating two or more six-ounce servings of fish and seafood each week is likely to have long-term benefits for most people.
“Most people” includes everyone except children younger than 12 and women who are pregnant, nursing or likely to become pregnant (see below). The IOM report was bolstered by another study, “Eating Fish: Health Benefits and Risks,” also published last month in the Journal of American Medical Association (JAMA).
“These reports dispel confusion that arose in recent years as more and more studies touted the health benefits of seafood while others raised caution because of toxic chemicals that can accumulate in these foods,” says Noel C. Borck, LHSFNA Management Co-Chairman.
Benefits and Risks
Studies presented by the American Heart Association show that the omega-3 fatty acids that are common in fish and seafood contribute to better cardiovascular health. They are associated with a decreased risk of sudden death and arrhythmia (irregular heart beat), decreased thrombosis (blood clots), decreased triglyceride levels, less growth of plaque and lower blood pressure. In cold-water fish, these acids keep the fish from freezing. In humans, they act as a natural blood thinner and anti-inflammatory.
Further, in a study published in July in the Archives of Ophthalmology, omega-3 fatty acids were found to reduce the risk of macular degeneration which can cause blindness as people age. Other preliminary investigations indicate that these acids may also reduce the risk of dementia, arthritis, asthma and kidney disease.
Despite these benefits, however, cautions have been raised about fish and seafood consumption because pollutants in sea water – most commonly, methyl mercury and PCBs (polychlorinated biphenyl) – frequently end up concentrated in the seafood that people eat. Though exact danger levels for these toxics are unknown, PCBs can reduce immune system function and thyroid levels, heighten certain cancer risks, disrupt reproductive function and affect early childhood development. Methyl mercury is linked to learning disabilities and developmental delays in children and to heart, nervous system and kidney damage in adults.
The Institute of Medicine’s report concluded that, except for young children and pregnant, nursing or may-become-pregnant women, the overall benefits outweigh the risks. Though virtually all fish and seafood contain significant omega-3 fatty acids as well as some contaminants (see comparison chart), salmon may be the single best overall choice because it is high in omega-3 yet generally low in mercury. However, the contaminant level of any sea animal is dependent on its own lifetime of food consumption. Thus, the report recommends that consumers who eat three or more fish and seafood servings per week mix in a variety of choices so they minimize the risk of higher contamination that may come from a one-track diet.
For pregnant women and their young children, the report encourages eating fish and seafood but restricting consumption to six to 12 ounces per week (one to two servings). It also recommends limiting canned albacore tuna consumption to six ounces and avoiding big predatory fish such as shark, swordfish, tilefish and king mackerel. These larger fish may have higher concentrations of methyl mercury built up from the consumption of smaller fish.
In general, by substituting a weekly serving or two of broiled, steamed or baked seafood for meat or poultry, consumers will reduce their intake of unhealthy saturated and trans fat and increase the intake of healthy omega-3. “That is certainly one of the benefits,” said David Bellinger, a professor of neurology at Harvard and a member of the committee that produced the report.
“These reports express a growing consensus in health and nutrition ranks that, despite some toxic risk, we can all benefit by eating more seafood,” says Borck. “Inevitably, as the U.S. and Canada embrace efforts to reduce obesity and enhance fitness, scientific investigation and debate will continue around this and many other food product issues. The LHSFNA will keep you abreast of ongoing developments.”
Chart courtesy of the Washington Post