|Fish oils in relation to blood cholesterol and cardiovascular diseases|
Dam, H.; Lund, E. (1962). Fish oils in relation to blood cholesterol and cardiovascular diseases, in: Heen, E. et al. Fish in nutrition. pp. 277-281
In: Heen, E.; Kreuzer, R. (1962). Fish in nutrition. Fishing News (Books): London. XXIII, 447 pp., more
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The relation of serum cholesterol to cardiovascular disease is still a subject for debate. As early as 1843, cholesterol was shown to occur in human atheromatous arteries. Subsequent investigators were able to induce atherosclerosis in rabbits and chicks by feeding them cholesterol. Epidemiological studies in various population groups drew attention to the relationships between high serum cholesterol levels, high incidence of coronary heart disease, and high fat intake. About 10 years ago, studies began stressing the importance of quality of dietary fat in influencing blood cholesterol levels. It was found that blood cholesterol in humans could be lowered by fats rich in polyunsaturated fatty acids, and fish oils were mentioned in this respect. Fish liver oils were found to be effective in lowering cholesterol levels; this effect is generally attributed to the high degree of unsaturation of their fatty acids, although some workers found that also vitamin A, in which some of those oils are rich, and the unsaponifiable fraction, exert a lowering influence in hypercholesterolemic patients. The high content of vitamins A and D in fish liver oils makes their common use, in prevention and therapy, quite risky, because of possible overdosage and toxicity from those vitamins. Fish body oils would therefore be preferable to fish liver oils. Of fish body oils, menhaden oil, although low in essential fatty acids, was found by Ahrens et al. to be more efficient than corn oil in markedly lowering serum cholesterol, phospholipids and triglycerides in a hyperlipemic and hypercholesterolemic patient. The authors observed the effect of menhaden body oil in two patients. A man and a woman with moderately elevated serum cholesterol levels were each given from 10 to 60 ml. per day of highly unsaturated triglycerides from menhaden body oil. This was in addition to an ordinary hospital diet providing 80 g. of fat per day. In the woman, some decrease in blood cholesterol was observed, especially when 60 ml. of menhaden oil were given, while in the man there was a less pronounced decrease. The results seemed to show that short periods of addition of moderate amounts of fish body oil to an ordinary diet containing other fats cannot a priori be expected to produce a drastic fall in serum cholesterol. In another series of experiments, 17 patients received an ordinary hospital diet for 21 days, then a "fish diet" for 28 days, and again the ordinary diet for 4 weeks. The authors found no differences in serum cholesterol values in the three periods. The mechanism by which polyenoic fatty acids influence the plasma cholesterol concentration is discussed. The authors conclude that more extensive study is desirable on the value of fish oils in the prophylaxis of cardiovascular disease.