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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.

Dietary experiments in which food was supplied in the form of a homogeneous liquid formula ration of definitely known composition have been performed on 171 subjects (159 men and 12 women, university students).During an initial period of 8 days all subjects ate the same ration and then groups of 8 to 12 individuals were given rations varying in respect of the fat moiety for a further 8 days. Plasma cholesterol analyses were performed at day 0, 4, 8, 12, and 16.The results obtained were interpreted as indicating that: firstly, there is no simple relationship between the hypocholesterolemic effect of an oil and degree of unsaturation; secondly, sitosterol or something closely associated with this sterol in the unsaponifiable matter accounts for a large part of the hypocholesterolemic activity of corn oil; and thirdly, certain fatty acids of short chain length or some other substance in butterfat and coconut oil have a hypercholesterolemic effect.

Three dietary experiments have been performed in which 36, 37, and 49 male medical students and staff members participated as experimental subjects. In each study, everyone consumed the same homogeneous formula diet for eight days at which time they were divided into five groups. One group was maintained on the original diet for a further eight days and the others were given diets varying in respect of the level and nature of the fat moiety. Protein supplied 16.9% of total calories in all experimental rations. In the first experiment, 37 subjects ingested a diet providing 58.5% of calories as corn oil. During the initial period the average of the individual percentage decreases in plasma cholesterol was 32.0 (P = < 0.01). Those continuing on corn oil displayed a further insignificant decrease. The others, receiving diets high in beef dripping, chicken fat, lard, and butter showed average individual percentage increases of 11.7 (P = > 0.05), 12.7 (P = > 0.05), 15.4 (P = < 0.01), and 28.8 (P = < 0.01), respectively. In the second experiment, 49 subjects consumed a fat-free diet for eight days. The average individual percentage decrease in plasma cholesterol was 22.2 (P = < 0.01). Those continuing on the fat-free diet showed little further change. Those ingesting 20 and 60% of calories as corn oil showed further percentage decreases of 6.9 (P = > 0.05) and 15.2 (P = < 0.01), respectively. By contrast, those receiving diets providing 20 and 60%, of calories as butterfat showed respectively percentage increases of 6.6 (P = > 0.05) and 21.7 (P = < 0.01). In the third experiment, 36 subjects ingested for eight days a diet in which butterfat provided 60% of calories. The plasma cholesterol level remained essentially constant, and did not change significantly in those continuing on this diet for a further eight days. The composition of the fat moiety in the remaining groups in terms of per cent calories derived from butter-fat and corn oil respectively was: 45: 15; 30: 30; 15: 45; and 0: 60. The averages of the individual percentage decreases in plasma cholesterol values were, respectively, 3.9, 15.9, 27.1, and 32.0. Except for the lowest of these values all the changes are highly significant (P = < 0.01). In addition to other conclusions that may be drawn from this work, these studies reveal that (1) there is a factor (or are factors) in certain animal fats that acts to elevate plasma cholesterol levels, and (2) there is a factor (or are factors) in corn oil that acts to depress plasma cholesterol levels.