Dietary Cholesterol and Plasma Cholesterol Levels in Man

Abstract

Sixty-three men and twenty women (university students) consumed a fat-free, homogeneous liquid formula ration for 8 days. Groups of 8 to 11 individuals were then transferred to diets in which 30% of the calories were supplied in the form of butter oil fractions which were substituted equicalorically for carbohydrate. The most volatile fraction, which was high in cholesterol (3.83%), caused a great increase in plasma cholesterol. The cholesterol-poor fractions led to relatively small increases but when supplemented with an amount of cholesterol equivalent to that provided by the cholesterol-rich fraction, increases of comparable magnitude were obtained. Supplementation of the fat-free diet with the completely saturated medium chain length triglycerides, C6–C12, derived from coconut oil with or without cholesterol, did not cause a significant increase whereas coconut oil did. These results have been interpreted as indicating that relatively small amounts of cholesterol, depending upon the nature of fat with which it is associated, can in fact effect highly significant increases in plasma cholesterol in man. It is suggested that the substance with which cholesterol reacts is a specific type of triglyceride having certain fatty acids attached at the alpha, beta, and alpha1 positions on the glycerol moiety.

Nutrient interrelationships of the fatty acids

“…This possibility was investigated by incorporating into a compounded diet at a level to supply 30% of the calories a fraction of completely saturated coconut-oil triglycerides containing fatty acids of chain length C,-C,,. Despite the absence of double bonds, this fat did not cause an increase in plasma cholesterol level when added to a fat-free diet; even when cholesterol was added, no increase in plasma sterol levels occurred (Beveridge et al 1959). Similar findings were subsequently reported by Hashim, Arteaga & Van Itallie (1960) and by Grande, Anderson & Keys (1961).…”

“…There is no doubt that the nature of the triglycerides and the constituent fatty acids of fats are in part responsible for their effects on plasma cholesterol level, but our work and that of Gordon, Wilkens & Brock (1958) demonstrate that degree of unsaturation is not the sole determinant and that certain other factors including the non-glyceride components also play a part. In experiments performed during the academic session of 1955-6 we obtained evidence that a hypercholesterolaemic factor in butter and a hypocholesterolaeniic factor in maize oil could be concentrated in the relatively volatile fractions obtained by molecular distillation of these fats (Beveridge, Connell & Mayer, 1957). Further work revealed that the cholesterol-rich distillate of butter was the most hypercholesterolaemic and that this was due at least in part to its content of cholesterol (Beveridge, Connell, Haust & Mayer, 1959).…”

“…I n 1954-5 we found that when butterfat was added to a fat-free diet in place of an equicaloric amount of carbohydrate, the plasma cholesterol level went up, whereas when maize oil was added to a fat-free diet at a level of 40% or more of calories there was a small but significant decrease in plasma cholesterol content (Beveridge, Connell & Mayer, 1956). These results, therefore, indicated that the third of the three possibilities correctly described the situation.…”

“…In experiments performed during the academic session of 1955-6 we obtained evidence that a hypercholesterolaemic factor in butter and a hypocholesterolaeniic factor in maize oil could be concentrated in the relatively volatile fractions obtained by molecular distillation of these fats (Beveridge, Connell & Mayer, 1957). Further work revealed that the cholesterol-rich distillate of butter was the most hypercholesterolaemic and that this was due at least in part to its content of cholesterol (Beveridge, Connell, Haust & Mayer, 1959). A similar result utilizing different fractionation techniques was subsequently reported for egg-yolk lipid by BronteStewart and his colleagues (Bronte-Stewart, 1961).…”

“…In the experiments designed to throw light on the nature of the hypocholesterolaemic factors in maize oil, vitamin E, at least in the form of a-tocopherol, was early eliminated as a possibility (Beveridge et al 1957). Results leading to somewhat divergent conclusions were obtained in attempts to assess the role of the polyunsaturated fatty acids.…”