Studies Conflict on Danger in Mercury-Laden Fish

By THE ASSOCIATED PRESS

wo studies have yielded contradictory findings about the possible heart dangers of eating mercury-laden fish.

The studies, reported in today's New England Journal of Medicine, looked at the long-term effects of mercury exposure on the hearts of middle-aged and elderly men.

One found no clear link between mercury levels in the body and the risk of developing heart disease; the other found that men who had suffered a heart attack had higher mercury levels than similar men who had not.

That left the researchers, Food and Drug Administration officials and other experts agreeing on just two things: more research is needed and people should not stop eating fish, because minerals and fatty acids in fish protect the heart. Also, many seafoods, like salmon and shrimp, contain little or no mercury.

"The bottom line is, yes, you should eat fish, and yes, you should know which fish have mercury" levels considered unsafe, said Dr. Daniel M. Shindler, a cardiologist at Robert Wood Johnson Medical School in New Brunswick, N.J., who was not involved in either study.

The F.D.A., the Environmental Protection Agency and many state agencies report such information. For years, they have warned women who are pregnant, nursing or of childbearing age to avoid fish from mercury-contaminated waterways, and also large predators like sharks and swordfish, which accumulate mercury from the smaller fish they eat. Research shows that mercury can harm the developing brain of a fetus or a child.

The American Heart Association, citing new research showing that omega-3 fatty acids in fish reduce the risk of heart disease, last week restated its guidelines that people eat at least two servings of fish a week, preferably fatty fish.

One of the New England Journal studies indicated that the mercury contamination in fish offsets the benefits of an important fatty acid, DHA.

Researchers at the Johns Hopkins Bloomberg School of Public Health reviewed data and tissue samples from an earlier cardiac study involving nine countries in Europe. They compared 684 middle-aged men who had had one heart attack with 724 similar men who had had none. They looked at the men's health histories, their use of tobacco and alcohol, and toenail clippings and fat withdrawn from their buttocks.

Toenails hold accumulated mercury, and fatty tissue accumulates DHA. The men's levels in each were measured. Those with the highest mercury levels were nearly 2.2 times more likely to have had a heart attack than were those with the lowest levels, Dr. Eliseo Guallar, an assistant professor of epidemiology at Hopkins, said.

Researchers at the Harvard School of Public Health studied 470 men who had had heart surgery or a heart attack, comparing each with a similar man without heart disease. Dr. Walter C. Willett, a professor of epidemiology and nutrition, said that mercury levels in the men's toenails corresponded well with the levels of fish they reported eating, but that his team found no association between mercury exposure and the risk of heart disease.

Dr. Willett and Dr. Guallar said there could be several explanations for their disparate results, including differences in the fish eaten in the United States and Europe and how the patients and comparison groups were selected in each study.

Both studies followed up a 1995 Finnish study that found an increased risk of heart disease in people whose hair had high mercury levels.