A fishy story?

A review of the literature on the health effects of dietary fish or fish-oil intake has a reassuring message for seafood lovers, anyone eating fish for health reasons, and perhaps most everyone else. Levels of mercury and other contaminants in commercially bought fish are low, and their potential risks are overwhelmed by likely reductions in cardiovascular mortality, according to an article in the October 18 issue of JAMA."The main message is really that everybody should be eating one or two servings of fish or seafood per week for their health," Dariush Mozaffarian, MD, from the Harvard School of Public Health in Boston, Massachusetts, told heartwire.

"Potential risks of fish intake must be considered in the context of potential benefits," according to Drs. Mozaffarian and Rimm. "Avoidance of modest fish consumption due to confusion regarding risks and benefits could result in thousands of excess CHD [coronary heart disease] deaths annually and suboptimal neurodevelopment in children."Those potential benefits are immense compared with the highly publicized but apparently low health risks associated with methylmercury, dioxins, and polychlorinated biphenyls (PCBs) that have been found in some fish species, the authors write. The evidence suggests a potential for neurodevelopmental deficits from early exposure to methylmercury, but the risk is likely diminished by limiting intake of fish with high methylmercury concentrations.And the cancer risk from consuming PCBs or dioxins in fish appears to be negligible, especially when stacked up against the likely cardiovascular protection, according to Dr. Mozaffarian. Moreover, he said, the evidence for CV [cardiovascular] benefit is far stronger than that for a cancer risk. "For benefits, we're talking about randomized trials and prospective studies in humans. For the risks, they're really theoretical risks based mostly on animal studies and a few limited studies in humans at much higher doses.""I think they've put things into perspective. This is an area that gets a tremendous amount of controversy and mixed messages going out to the public," Alice H Lichtenstein, MD, director of the Cardiovascular Nutrition Laboratory at the Human Nutrition Research Center on Aging at Tufts University in Boston, Massachusetts, told heartwire. The conclusions of Drs. Mozaffarian and Rimm, Dr. Lichtenstein said, are "well founded" and "consistent with what a lot of people have concluded that the benefits [of fish and fish-oil consumption] outweigh the risks."Benefits and Risks of Fish Intake for WomenThe report's recommendation that most everyone can benefit from a couple of servings of fish per week was directed not only to the general population and those with cardiovascular risk factors, but also to women who could become pregnant or who are nursing and are urged to avoid a few species of fish that generally have higher contaminant levels."I think it's important that women of childbearing age and nursing mothers not worry so much about mercury, which is present at high levels really in only four fishes that they're not supposed to eat," Dr. Mozaffarian said.

One major caution in the report is for people who eat fish that is not purchased from commercial sources. "Some of the inland lakes in the United States are more highly contaminated with PCBs and dioxins," Dr. Mozaffarian said, "so someone who sports fishes and eats their catch frequently should consult regional advisories about what levels of PCBs and dioxins are in the different fish." Another caveat: "Anybody who eats fish at one or more servings per day, just to be on the safe side, should make sure they're eating a variety of different fish, making sure that at least some are lower in mercury levels," Dr. Mozaffarian said.