The effect of vegetable fat ingestion on human serum cholesterol concentration.

In 3 healthy male physicians a reduction of dietary fat produced a significant fall in the serum cholesterol concentration. Subsequently, when a diet containing normal quantities of fat but very low in cholesterol was taken, a rise in serum cholesterol concentration occurred in all 3 subjects. W HILE controversy has long prevailed concerning the possibility of lowering serum cholesterol by regulation of the diet,'-3 there is now ample evidence that in most individuals the serum cholesterol concentration will fall if the intake of fat is sufficiently restricted.3'7 Some investigators believe that the chief reason for this chemical alterations is that a low-fat diet automatically restricts the ingestion of cholesterol.8 However, animal experiments suggest that the dietary fat level, per se, is more important than is the dietary cholesterol level in changing the serum cholesterol concentration.9'-3 Our experiments were designed to discover whether human serum cholesterol concentration can be affected by a diet low in cholesterol but of normal fat content. Since there is evidence that vegetable fats contain no cholesterol whatsoever and since sterols found in plants are not absorbed or converted into cholesterol in significant amounts by animals,9' 0 13 it seemed worthwhile to investigate the effect of vegetable fat on serum cholesterol concentration. Evaluation of the effect of diet on serum cholesterol concentration requires studies over a considerable period of time. In view of the difficulties of conducting prolonged studies on patients, three of the authors served as subjects. One of the authors (subject 2) constantly had a level of serum cholesterol which exceeded the normal. The other 2 subjects had much lower values and were always within the normal range of serum cholesterol concentration. One of the authors, a trained dietitian, designed and supervised the diets. Therefore 3 of the authors subjected themselves to strict diets for three to eight months. Each was studied; first on his customary diet, second when both fat and cholesterol were greatly restricted, and third, when through a diet containing vegetable fats, cholesterol was restricted but fats were normal in amount. The serum cholesterol was estimated on samples taken twice weekly during these periods by a method previously described.3 The normal range of values for this method agrees with those recently reported by Keys.'4 The results showed that the serum cholesterol concentration was always decreased by dietary restriction of both fat and cholesterol, but that it again approached the control level when …