By LEE BOWMAN
October 18, 2006
The reports, based on reviews of previous research, suggest that Americans generally would benefit from eating a little more fish, rather than less.
"Overall, for major health outcomes among adults, the benefits of eating fish greatly outweigh the risks. Somehow, this evidence has been lost on the public," said Dr. Dariush Mozaffarian, an instructor in epidemiology at the Harvard School of Public Health and lead author of a review published Wednesday in The Journal of the American Medical Association. The National Heart, Lung and Blood Institute sponsored that study.
A second study, produced by the Institute of Medicine, was slightly more cautious. It supports government dietary advice that fish should be part of a healthy diet, but said that given the potential risks from exposure to contaminants, some limits are in order, particularly for women who are or may become pregnant or who are breastfeeding.
A 12-member expert panel set up under a contract with the National Oceanic and Atmospheric Administration and the Food and Drug Administration produced that report.
Both reports drew criticism from food-safety and environmental groups that felt the researchers - and the makeup of the Institute of Medicine panel - tilted in favor of the seafood industry and promoting greater fish consumption with too few caveats.
"The bottom line is, the IOM report complicates the issue rather than clearing anything up," said Jennifer Sass, a scientist with the Natural Resources Defense Council.
Malden Nesheim, a professor emeritus of nutrition at Cornell University and chairman of the Institute of Medicine committee, said the panel actually found slim evidence for many claims about the health benefits of fish as well as the dangers. "We were surprised at the lack of reliable data on the distribution of contaminants in our seafood supply or on how the benefits might counteract the risks," he told reporters.
However, both groups of researchers agreed that eating fish and shellfish can reduce a person's overall risk for developing heart disease. The Harvard review found that fish consumption lowers the risk of death from heart disease by 35 percent.
"We also found that fish or fish oil intake reduces total mortality by 17 percent, a remarkable reduction considering that this is the benefit for deaths from all causes," Mozaffarian said.
The biggest concern about seafood consumption over the past several decades has involved exposure to methylmercury, a heavy metal linked to learning disabilities and developmental delays in children and to heart, nerve and kidney damage in adults.
"The controversy has been pretty one-sided, dominated by those who feel low levels of mercury impair cognitive development," said Dr. Gary Myers, a neurologist at the University of Rochester in New York. He was involved in one of the largest studies tracking prenatal mercury exposure from fish against long-term development, but not part of the two studies released Tuesday. "Now, we seem to be looking a little more at the more general issues of nutrition from fish."
Studies have also shown that omega-3 fatty acids and several other key nutrients from seafood contribute to early brain development in infants.
Because large predatory fish, like king mackerel, sharks and swordfish, eat smaller fish and absorb mercury from them, the researchers echoed government advice that women of childbearing age, nursing mothers and young children avoid those fish.
But the Institute of Medicine committee said those groups should eat at least two servings (6 ounces) of fish a week, and can safely consume up to 12 ounces. The report said that those groups could eat up to 6 ounces of (canned) white albacore tuna a week. The FDA recommends that young children get smaller portions.
The committee said evidence about other types of contamination, such as PCBs and dioxins linked to cancer, is so limited that there's little cause for concern if people eat the recommended number of servings a week. The best approach is to try to eat a variety of fish from week to week.
Still the committee didn't say how government officials should go about reducing consumer confusion about fish.
"If they really wanted to help high-risk consumers and bring others back to the fish counter, the panel would have supported posting information on mercury in stores, like those that are already being posted by some grocery chains," said Caroline Smith-DeWaal of the Center for Science in the Public Interest, a food watchdog group.
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