Fish, Fatty Acids and Physiology; Fish, Long Called Brain Food, Turns out to Be Heart Food as Well
Dusheck, Jennie, Science News
Eskimos have a lower incidence of heart disease than do other populations, even though their high-fat, high-cholesterol diet ought to make them a high-risk group for heart disease. How do the Eskimos get away with it?
The answer lies in the kind of fat they eat. The Eskimo diet consists mostly of fish, seal and whale. Fat from these animals contains "omega-3 fatty acids," which are structurally distinct from the "omega-6 fatty acids" that most Westerners get from domestic meats. Epidemiologic studies of populations, such as the Eskimos and Japanese, that consume a lot of fish suggest that the omega-3 fatty acids in fish reduce the likelihood of getting heart disease, rheumatoid arthritis and other inflammatory diseases (SN:5/11/85:, p. 295).
This finding, combined with increasing knowledge about a class of compounds called eicosanoids, has brought many nutritionists and biochemists to a pitch of excitement. Eicosanoids, which are derived from fatty acids, regulate communication between cells and, consequently, inflammation and other immunological responses.
About 150 scientists convened in Washington, D.C., last June for a three-day conference on the health effects of polyun-saturated fatty acids in seafood and struggled to decide what is really known about fatty acids and eicosanoids. They focused mainly on how omega-3 fatty acids may function to reduce the incidence of heart disease, what other effects they may have on health and what quantity of omega-3 fatty acid should be recommended for a normal diet or a therapeutic dose.
"The excitement we feel about the possible uses of seafood is balanced by a rather sobering awareness of our ignorance," says William Lands, head of biological chemistry at the University of Illinois in Chicago and a cochair of the conference.
Ignorant or not, the scientists brought to the conference a wealth of iformation. Both epidemiologic and clinical studies suggest, they said, that the consumption of fish, fish oils or omega-3 fatty acid supplements may reduce the likelihood of developing atherosclerosis, thrombosis, rheumatoid arthritis, migraine headaches and possibly even multiple sclerosis. On the other hand, the consumption of large amounts of fish oil may have unknown detrimental effects. For example, though the Eskimos and Japanese have less heart disease than other groups, they also suffer far more strokes.
Fish oil's diverse effects appear to come about through several routes. To begin with, fatty acids, which bond to glycerol to make up fats, are broadly distributed in the body. Fats, in general, are important sources of energy; they insulate the body and certain organs; and they are a major component of nerve tissues, reproductive tissues and cell membranes. Many kinds of fatty acids are essential to the human diet. A deficiency of essential fatty acids can result in skin inflammation and impaired transport of lipids. Laboratory animals on fatty-acid-deficient diets also exhibit poor growth, infertility and susceptibility to stress. But most studies of such deficiencies have focused on omega-6 fatty acids.
Fortunately, except in the case of people fed intravenously for long periods, fatty acid deficiencies are extremely rare in humans. Only 1 or 2 percent of the total calories in a diet need to come from essential fatty acids, said researchers at the conference, and all normal Western diets contain far more than that. In fact, fats make up about 40 percent of the calories in the average U.S. diet -- about twice what is necessary. However, these fatty acids are mostly omega-6s, and we seem to need some omega-3s as well.
Though there is no proof that omega-3s are essential for human development, a number of studies suggest their importance. Rats reared on omega-3-deficient diets suffered impaired vision and reduced learning ability, according to a paper presented in 1976 by M.S. Lamptey and B. …