Certain studies indicate that almost all individuals over 30 years of age in Western Europe and the United States have some degree of atherosclerosis. 1
This situation should alarm us when we realize that myocardial infarction (heart attack), angina pectoris (heart pain), peripheral vascular insufficiency, and cerebral ischemia (stroke) stem from atherosclerosis. Consequently, in affluent societies the major contributor to death is restricted circulation to the brain, heart, kidneys, and limbs.
Extensive evidence indicates a high serum cholesterol level greatly increases the risk of developing coronary heart disease. A diet high in animal or saturated fat increases the serum cholesterol level, while a diet containing the polyunsaturated (or vegetable) oils tends to lower the serum cholesterol.
Four extensive investigations have dealt with the prevention of coronary heart attack by dietary changes.2 Three of these, the New York Anti-coronary Club study, the Finnish Mental Hospital Study and the Los Angeles Veterans' Administration Domiciliary Center Study involved replacing a large part of the saturated fat in the diet with polyunsaturated fat, however, with out significantly reducing total fat intake. The fourth study, the Chicago Coronary Prevention Evaluation Program, involved a reduction of total fat intake to about 30 percent of the daily calorie consumption, and correlated this factor with other life-style changes such as weight control, smoking habits, hypertension, and exercise. The combined findings of these four studies indicate that a change in living habits, particularly diet, is associated with decreased incidence or mortality from coronary heart disease.
Many dietary intervention studies have used patients who have already experienced their first heart attack, with the intent of preventing subsequent attacks or fatalities. 3 The earlier studies, which used diets low in fat (10-25 percent of total calorie consumption), report a marked reduction in coronary mortality.
In the late 1950's and 1960's the use of polyunsaturated fat became a part of the dietary intervention studies. As an example, an eleven-year study, reported by Leren from Oslo in 1970,4 involved 206 men in an experimental group. Thirty-nine percent of the total calories in the diet consumed by this group was fat, with 50 percent of these fat calories coming from polyunsaturated fat. The study showed a survival rate of 80.5 percent for this dietary treatment group, compared to the usual survival rate of 66.1 percent. Thus it appears that even a diet with a fat intake of up to 39 percent of total calorie consumption is beneficial when a liberal amount of polyunsaturated fat is included.
A study of the regression of atherosclerosis in monkeys has also been a productive means of studying the effect that both the type and the quantity of fat in the diet has on atherosclerosis. Monkeys with extensive atherosclerosis have been fed a diet in which 4 percent of the total calories was in the form of fat. Another group of monkeys with the same extensive atherosclerosis were given a diet in which corn oil formed 40 percent of the total calories. The reduction of arterial cholesterol and the regression of the atherosclerosis was the same for both fat levels studied. 5, 6 Likewise, when monkeys with well-developed atherosclerosis were fed diets containing 10 percent of total calories as vegetable fats or 40 percent of total calories as safflower oil, the rate of lesion regression was essentially the same. 7 Thus we can conclude that if the diet contains a highly unsaturated fat (such as corn, cottonseed, safflower oil, et cetera) a severely restricted intake of fat is not necessary in order to obtain regression of atherosclerosis.
How much fat should we as humans be consuming? The Dietary Goals for the United States, prepared by the Select Committee on Nutrition and Human Needs, of the United States Senate (Feb. 1977), recommends 30 percent of the total calories as fat, with one third of these fat calories being polyunsaturated, one third being saturated, and the remaining one-third representing oleic acid or the monoenes. For most Americans, to follow this recommendation would mean reducing their total fat consumption by about 25 percent and a reduction in their intake of meat, which contains the highly saturated fats. This reduction can be accomplished by the consumption of larger quantities of vegetables and fruits.
Linoleic acid, an essential fatty acid, is an important ingredient of the polyunsaturated fats. The body uses linoleic acid to make a hormonelike group of substances called prostaglandins. These prostaglandins have been shown to have extensive physiological effects in the control of blood pressure, in stimulating heart action, in controlling blood clotting, and in regulating the metabolism of carbohydrates and fats. Linoleic acid also is important in control of serum cholesterol. In fact, a diet high in polyunsaturated fat is more effective in lowering serum cholesterol than is a diet that has a severe restriction on quantity of fat. According to the available information, the moderate intake of fat (30 percent of total calories as cited above) with a liberal content of vegetable oils is conducive to good health. And isn't good health a goal worth the minor sacrifice of making needed adjustments in eating habits?
1 D. H. Blankenhorn, Diet and Atherosclerosis, edited by C. Sirtori, G. Ricci, and S. Gorini (New York and London: Plenum Press, 1973), p. 119.
2 J. Stamler, British Heart Journal, Suppl., 33, 145 (1971).
3 S. Heyden, The Role of Fats in Human Nutrition, edited by A. J. Vergroesen (New York- Academic Press, 1975), p. 71.
4 P. Leren, Circulation 42, 935 (1970).
5 M. L. Armstrong and M. B. Megan, Circ. Res. 30, 675 (1972).
6 M. L. Armstrong, E. D. Warner, W. E. Connor, Circ. Res. 27, 59 (1970).
7 R. N. Chakravarti, B. S. Kumar, C. R. Nair, M. Kumar, Atherosclerosis 28, 405 (1977).