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A new Harvard study knocks a big hole in the notion that eating lots of fish guards against heart disease.

Eating a little may be better than eating none, but after tracking nearly 45,000 men for six years, researchers found that those who ate six or more helpings of fish a week had as many heart attacks and other signs of coronary disease as those who ate only one helping a week."For people who like fish, sure, eat it," said Dr. Alberto Ascherio, an assistant professor of nutrition and epidemiology at the Harvard School of Public Health and the report's lead author.

"But it appears that high frequency of fish in the diet does not add measurably to increased protection against heart disease," Ascherio said.

The report, appearing in Thursday's New England Journal of Medicine, comes 15 years after researchers first suggested that Eskimos in Greenland have such healthy hearts because their diets are so heavy on fish, seals, whales and other marine life.

That study, soon backed by other reviews and experiments, triggered wide belief among some scientists as well as lay people that fish contain substances that protect against heart attacks. Sales of fish oil extracts, particularly those containing the suspected protective material, omega-3 fatty acids, soared.

But the new report concludes that if eating fish helps hearts at all, it does not take much. And it suggests that other factors may explain the low rates of heart disease found among Eskimos, Japanese and other peoples with diets high in fish.

The Harvard study is part of a major, ongoing examination of the health and living habits of 44,895 male health researchers - most of them dentists - begun in 1986. It found that men who ate some fish were 25 percent less likely to get heart disease than those who ate none.

"A little fish may do some good, but more fish is not necessarily better," Dutch researcher Martijn B. Katan wrote in an editorial accompanying the Harvard report. But the new study, said Katan, "offers no support for the blanket use of fish-oil capsules."