Fish Linked to Cardiac Health : Dutch Study Shows Diet May Reduce Heart Attacks

Dutch researchers who studied a group of middle-aged males for 20 years have concluded that those who ate at least a pound or two of fish a week ran a better than 50% lower risk of dying from heart disease than those who consumed no fish.

The study, published in today’s New England Journal of Medicine, provides the strongest evidence to date that fish contain some substance that appears to reduce the risk of heart attacks.

The scientists, from the Institute of Social Medicine at the University of Leiden, began their study in 1960 when their 872 subjects were aged 40 to 59.

After excluding any subjects with known heart disease and conducting detailed analyses of each man’s weekly diet, the researchers followed their subjects for the next 20 years. By the end of the study in 1980, 78 men had died from coronary heart disease.

Five Categories

The subjects had been divided into five categories based on the amount of fish consumed per day. The average fish consumption was about five ounces a week, but some consumed none and others said they ate more than a pound a week.

The scientists reported that the more fish the individual ate, the less likely were his chances of dying of heart disease. For example, the mortality rate for those who consumed at least 14.7 ounces a week was less than half that of those who ate no fish.

The researchers said that by using special methods of statistical analysis, they were able to eliminate such other risk factors as cigarette smoking or high blood pressure and thus show the direct correlation between fish consumption and heart disease mortality.

Cancer Question

This correlation led the researchers, headed by Dr. Daan Kromhout, to conclude that “the consumption of as little as one or two fish dishes per week may be of preventive value in relation to coronary heart disease.”

In an accompanying editorial, Dr. John A. Glomset of the University of Washington School of Medicine said that although the link between fish and preventing heart disease appears to be strong, there is still a question about whether people who eat fish run a greater risk of developing cancer.

“I would like to know what these men (the fish eaters) did die of,” Glomset said in a telephone interview, noting that other scientists have accumulated tentative evidence that the polyunsaturated fats found in fish may cause cancer when consumed in large amounts. “Was it cancer? It remains to be determined whether eating fish has a deleterious effect.”

The Dutch researchers reported that of a total of 1,088 men followed for 20 years--872 in the study group plus a smaller group of 216 who took part in a related study--132 died of cancer, 110 from coronary heart disease and 33 from strokes. They did not provide any data to show how the cancer deaths correlated with fish consumption.

Eskimos, Japanese

Until their study, the chief evidence for a low heart death rate among fish eaters has come from studies among Eskimos and Japanese--both of whom eat large amounts of fish and have mortality rates from heart disease far below that of Americans.

Scientists have been trying to identify the substance in fish that seems to lower the risk of heart attack. This substance appears to be a constituent of the polyunsaturated fatty acids in fish, which differ from the polyunsaturated fatty acids in vegetable oils. The identity of the substance and how it works are still not clear.

“The take-home lesson for the public is that we need to do more research,” Glomset said. “The take-home lesson for physicians is we are learning that not all polyunsaturated fats are the same. That lesson needs more attention.”