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CORVALLIS, Oregon -- Though some species of fish around the world's are likely to be contaminated with mercury, PCBs and other toxins, the benefits of eating seafood continue to outweigh the risks, a panel of scientists recently said at the annual meeting of the American Association for the Advancement of Science.
"The best science coming out over the last two years has overwhelmingly been in favor of the benefits of seafood consumption," said Michael T. Morrissey, director of Oregon State University's Seafood Laboratory in Astoria, Ore., and moderator of the panel.
Phillip Spiller, director of the Office of Seafood for the U.S. Food and Drug Administration, said that the FDA is going through a risk/benefit analysis to establish effective guidelines for fish consumption. Historically, he said, the agency has looked almost exclusively at safety issues without taking benefits into consideration.
"We must formulate a clear message for the consumer," he said.
And that is where things get complicated, pointed out Morrissey, who also is a professor in OSU's Coastal Oregon Marine Experiment Station. More research is necessary to determine exactly what the risks and benefits of eating seafood may be.
During the AAAS panel, for example, Phil Davidson from the University of Rochester Medical School, presented results of a unique 10-year study of more than 700 children living in the Seychelles Islands. The children's mothers averaged 12 meals of fish a week – about 10 times the average fish consumption of individuals in the United States – and those fish contained high levels of methylmercury.
Yet cognitive tests on the children, taken multiple times over the years, found no cognitive defects or other maladies normally attributed to mercury absorption.
"Those results are fascinating," Morrissey said in an interview after the panel discussion. "Is there something beneficial in consuming the fish that negates any adverse effects of the mercury? The science isn't quite there yet. But it underscores the importance of looking at the issues holistically instead of formulating conclusions based on scattered evidence."
There are some seafood products where caution is warranted, Morrissey pointed out. Guidelines set by the FDA and the Environmental Protection Agency for young children and pregnant women should be followed, he advised.
"If you're in that group, avoid eating shark, swordfish, tilefish and Spanish mackerel," Morrissey said. "But young children and pregnant women should still eat 12 ounces a week of a variety of fish to be sure to get the important nutrients – especially omega-3 fatty acids.
"For the rest of us," he added, "I would recommend eating fish 4-7 times a week. The evidence still suggests that seafood plays a role in reducing coronary heart disease – and new studies suggest that it may reduce the onset of Alzheimer's as well as other mental illnesses."
Those guidelines were echoed by Michael Crawford of the Institute of Brain Chemistry and Human Nutrition at the Metropolitan University in London.
"There is more and more evidence showing the role of seafood consumption in brain evolution, development and mental health," he said.
Among the important nutrients for pregnant women and new mothers is a specific fatty acid found only in fish oil, docosahexaenoic acid, or DHA, panelist Susan Carlson told the AAAS. Carlson, from the University of Kansas Medical Center, said DHA has been linked with visual and cognitive acuity in fetuses and newborn infants who have been breast-fed.
And women in the United States typically consume less DHA than most other groups around the world, she added.
Carlson and Steve Otwell, from the University of Florida, both spoke as panelists at the AAAS forum and are part of a panel commissioned by the National Academy of Science that will deliver a report on seafood consumption later this spring.
Otwell warned the AAAS gathering that as seafood consumption continues to rise, the demand may overcome the supply. On a world scale, he said, there may be a shortfall of up to 10 million metric tons by 2010. And despite rapid growth, aquaculture has yet to fill the gap.
Despite the demand, many groups – particularly in the United States – still shy away from consuming seafood, the panelists pointed out.
Joyce Nettleton, a private consultant and science writer, said that Americans are particularly "risk-averse" when it comes to food scares.
"What people hear about the hypothetical risk of eating fish laced with contaminants bears little relation to the scientific evidence," she said.