Heart disease: let them eat fish.

If fish had the ability, they might be blushing from all the plaudits heaped on them by researchers this week.

Two reports in the May 9 NEW ENGLAND JOURNAL OF MEDICINE (NEJM) say that oil from fish can prevent heart disease. The studies back up earlier findings that Greenland Eskimos, who eat a lot of fish, have a low risk of heart disease despite a high-fat, high-cholesterol diet. A third NEJM article suggests that the oil may work its magic through an antiinflammatory effect. And according to work presented at the American Federation for Clinical Research (AFCR) meeting this week in Washington, D.C., fish oil may also alleviate migraine headaches and rheumatoid arthritis.

In 1960, Dutch researchers from the University of Leiden asked 852 men and their wives what the men were eating, then kept track of the men for the next 20 years. Though the researchers found no relationship between fish consumption and such established heart disease risk factors as blood cholesterol level and blood pressure, they found the more fish a man ate, the less likely he was to die of heart disease.

The death rate from heart disease was more than 50 percent lower among men who ate at least 30 grams (1 ounce) of fish per day compared with men who ate no fish. Just one or two fish dishes a week, the researchers say, "may be of value in the prevention of coronary heart disease," and they suggest that dietary guidelines include this recommendation.

The probable key is the action of fatty acids in fish oil (also found in leafy vegetables and soy, walnut and rapeseed oils) called omega-3. These fatty acids alter metabolic pathways in the body, discouraging the formation of heart-attack-causing blood clots. What remains to be studied, notes John A. Glomset of the University of Washington in Seattle in an accompanying editorial, "is whether the consumption of fish also correlated, perhaps unfavorably, with mortality from cancer and other diseases."

The second NEJM report came from the Oregon Health Sciences University in Portland. Twenty people with high triglyceride levels--a factor in hear disease--rotated among diets containing fish oil, polyunsaturated vegetable oil or low-fat foods. The fish oil, which is a type of polyunsaturated fat, significantly lowered both cholesterol and triglyceride levels, leading the researchers to conclude that fish oils and fish may by useful treatments for high triglyceride levels. Omega-3 fatty acids reduce the synthesis of a molecule that carries triglycerides and cholesterol through the blood, and increase cholesterol excretion, they say.

Harvard University researchers studied the effect of fish oil on the immune system. In seven healthy men they supplemented the usual diets with fish oil, and found the men produced less active white blood cells, in a way "desensitizing" the normal inflammatory response. This inflammatory response has been linked to atherosclerosis. Glomset, one of the originators of the theory, notes that limiting it may limit atherosclerosis.

Moving from the heart to the head, University of Cincinnati researchers reported at the AFCR meeting that fish oil ingestion led to a reduction in migraine intensity compared with placebo in six of eight subjects. Omega-3 fatty acids reduce two factors associated with migraines -- serotonin, which acts on cerebral blood vessels, and platelet aggregation--and they relax blood vessels, but exactly how they work remains to be determined, says University of Cincinnati researcher Charles Glueck.

If brain and heart, why not joints? Albany (N.Y.) Medical College researchers reported that 23 people on fish oil had less morning stiffness than 21 people on placebo--suggesting, they say, that more studies are warranted.