An earlier version of this article quoted Harvard School of Public Health cardiologist Dariush Mozaffarian on the benefits of eating salmon, saying that eating "one to serving per day of farm-raised salmon" will help meet the recommendations for consumption of healthful omega-3 fatty acids. That now reads "one to two servings per week."
Benefits of Fish Exceed Risks, Studies Find
Wednesday, October 18, 2006
The health benefits of eating fish regularly outweigh the danger from mercury and other contaminants even for pregnant women and children, two major reports concluded yesterday as scientists tried to resolve a slippery question that has long vexed consumers.
The findings, which were reached by independent teams of scientists, pointed to significant benefits for both young and old. In adults, the death rate from heart disease was 36 percent lower among those who ate fish twice a week compared with those who ate little or no seafood, according to a study being published today in the Journal of the American Medical Association. Overall mortality was 17 percent lower, the study by Harvard School of Public Health researchers found.
A second, federally funded report released by the Institute of Medicine (IOM) echoed the conclusion that the heart benefits of eating seafood outweigh the risks and said infants also benefit from the healthy fats found in seafood.
Omega-3 fatty acids found in fish promote healthy vision and brain development in infants whose mothers consume fish or seafood during pregnancy or while nursing, the report said. These healthy fats also appear to decrease the risk of delivering a preterm, low-birth-weight baby.
Even so, because of methyl mercury concerns, the IOM report stuck with the current federal guidelines that advise women who are nursing, pregnant or plan to become pregnant, as well as children age 12 and younger, to refrain from eating swordfish, shark, tilefish and king mackerel. These two groups can safely consume up to 12 ounces of other fish per week, the report said, but they should also limit white (albacore) tuna to six ounces a week because of its high levels of methyl mercury, which can be toxic to the brain and hearing.
The new findings are expected to help put to rest a hotly debated nutritional debate that often left perplexed consumers asking, "What do I do about fish?"
"Having this report will be really good," said Walter Willett, a professor of epidemiology and nutrition at the Harvard School of Public Health, who was not a co-author of either study.
Environmental groups echoed that assessment.
"Overall, they are reasonable recommendations," said Rebecca Goldburg, a senior scientist with the nonprofit advocacy group Environmental Defense who reviewed the IOM report before its release.
But Goldburg and others also raised concerns about the impact the findings could have on marine life if people worldwide try to dine on seafood twice a week, because there isn't enough to go around. Goldburg, who regularly serves her own family seafood, urged consumers to make smart choices "that are good for their health as well as for the oceans. If we want fish to be abundant, choose seafood that is farmed or fished in an environmentally responsible manner."
Although the new findings may help to settle the question of the risks of eating seafood, there is still disagreement about the extent of the health benefits. A study published earlier this year in the British Medical Journal found no overall reduction in mortality, no decrease in heart disease risk and no reduction in cancer from consuming omega-3 fatty acids.
Goldburg said, "I feel quite comfortable with the evidence that seafood is good for you but am a little taken aback by the conclusion that the benefits are as sweeping as in the JAMA study."
Other recent studies have hinted that omega-3 fatty acids may also help protect against diabetes and cancer, slow the progression of early Alzheimer's disease, and perhaps ameliorate depression and other mental disorders, including attention-deficit disorder in children. But the IOM report found that the evidence of those benefits is unclear, and the Harvard study did not address those questions.
Both reports found little evidence to fuel concerns that eating fish exposes people to large amounts of dioxins, polychlorinated biphenyls (PCBs) and other harmful organic chemicals that have been linked to seafood consumption.
Experts hope that the findings will end the confusion that often occurs at seafood counters and in restaurants.
"Consumers need better guidance on making seafood choices," said Malden C. Nesheim, chair of the committee that wrote the IOM report, which was sponsored by the National Oceanographic and Atmospheric Administration and the Food and Drug Administration.
The findings of both reports are consistent with current recommendations of the U.S. Dietary Guidelines and the American Heart Association, which advise eating two meals -- roughly three ounces per serving -- of seafood per week.
By simply substituting broiled, steamed or baked seafood -- especially fatty species such as salmon -- for meat or poultry a couple of times per week, consumers can increase their intake of omega-3s and help reduce the amount of unhealthful saturated and trans fat they eat.
People need "a quarter-gram per day on average [of omega 3s], so one to two servings of cod per week will not get you there," said Dariush Mozaffarian, a Harvard cardiologist and co-author of the JAMA study. "On the other hand, one to two servings per week of farm-raised salmon will."
Large, federally funded nutritional surveys suggest that most people do not get enough omega 3s.
"About 75 percent of women of childbearing age and about 85 percent of pregnant women consume less than six ounces of seafood per week," noted Mozaffarian. Omega 3s cross the placenta and help build developing brains in fetuses and in infants during the first months of life.
"That certainly is one of the benefits," said David C. Bellinger, a professor of neurology at the Harvard School of Public Health and a member of the IOM committee.