There is no shortage of old wives' tales about the virtues of eating fish: it is "brain food," according to legend, and cod-liver oil is a cure for all that ails. The wives may have been onto something. Eating a little fish a day may indeed keep the doctor away, particularly the cardiologist. That is the implication of three new studies published in the New England Journal of Medicine.
The largest of the studies, conducted in the Netherlands, found a direct link between the amount of fish in the diet and the rate of death from heart disease. Investigators monitored the eating habits of 852 middle-aged Dutchmen for 20 years and found that the incidence of fatal heart disease was more than 50% lower among men who regularly ate fish than those who ate no fish at all--despite the fact that the fish eaters consumed somewhat more cholesterol and more meat than non-fish eaters.
The fish factor in heart disease is not entirely new: Greenland Eskimos, who eat about 14 ounces of fish every day (more than the average American eats in three weeks), are known to have a remarkably low incidence of heart disease. But the Dutch study suggested that even modest doses of seafood, the equivalent of one or two fish dishes a week, "may be of value in the prevention of coronary heart disease."
Researchers are only beginning to fathom the complex biochemical reasons for this effect. Fish, specifically such cold-water species as cod, salmon, sardines and mackerel, contain certain polyunsaturated oils that are found in no other foods and have profound effects on body chemistry. A diet rich in these fats reduces the tendency of blood to clot, much the way that aspirin does; it also helps lower the level of cholesterol in the blood. Both effects could help explain the low rate of heart disease in Eskimos.
The two accompanying studies in the New England Journal focused on how a fish diet affects the body. Researchers at the Oregon Health Sciences University in Portland found that adding salmon oil to the diet seems to help lower the levels of triglycerides and a type of cholesterol known as VLDL (very-low-density lipoprotein) in patients with high levels of these potentially dangerous fatty substances. According to Dr. William Connor, who headed the study, as much as 30% of the adult American population has high levels of these fats. In the past, these people have been advised to avoid fatty fishes like salmon. But, the researchers noted, "consumption of such fish may have a therapeutic benefit."
The third study held implications not only for heart disease but possibly for such ailments as rheumatoid arthritis and asthma. The research, conducted by Harvard scientists, indicated that a fish diet may slow the process of inflammation by altering the chemistry of white blood cells. Preliminary evidence both in animals and humans suggests that such a diet may help relieve symptoms of arthritis and perhaps other inflammatory diseases. However, says Dr. K. Frank Austen of Harvard, it is too early to make any recommendations, and fish-oil experts sound a special note of caution on cod-liver oil, which can be toxic in high doses.