The Effect of Partial Hydrogenation of Dietary Fats, of the Ratio of Polyunsaturated to Saturated Fatty Acids, and of Dietary Cholesterol upon Plasma Lipids in Man *

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Abstract
Forty-two healthy men were divided into 7 groups and maintained for 20 weeks on formula diets. During this time the effects of the following dietary fats on plasma lipid levels were determined: Fat A, a partially hydrogenated soybean oil; Fat 3, a blend of vegetable fats similar to Fat A in saturated and mono- and polyunsaturated fatty acid content but containing no hydrogenated fat; Fat C, a mixture composed of Fat A and cocoa butter; Fat D, a mixture composed of Fat B and cocoa butter, and Fat E, cocoa butter. The diets containing these fats had P/S ratios of 1.6, 1.5, 0.7, 0.7, and 0.1, respectively. Fats A and B were fed both with and without dietary cholesterol in the form of dried egg yolk powder. All of the other fats were fed only in cholesterol-free diets. Addition of cholesterol (average of 742 mg daily/subject) to diets containing Fat A or Fat B significantly increased the plasma cholesterol levels, 23.8 and 26.6 mg/100 ml, respectively. The plasma cholesterol response to the partially hydrogenated fat (Fat A) was identical to that of the unhydrogenated fat (Fat B), whether or not cholesterol was included in the diet. A reduction in the P/S ratios of cholesterol-free diets containing Fats A and B from 1.6 and 1.5, respectively, to 0.7 by the addition of cocoa butter had no effect on the plasma cholesterol response. In the cholesterol-free diets, cocoa butter produced an average plasma cholesterol level not significantly different from that obtained with the fat having the highest P/S ratio. We conclude that with a cholesterol-free formula diet the plasma cholesterol level is unaffected by variation in the (P/S ratio of the diet from 1.6 to 0.1. The plasma phospholipid values, like the values for cholesterol, were highest when the diet contained cholesterol. With the cholesterol-free diets the plasma phospholipid values produced by the ingestion of cocoa butter were somewhat higher than those obtained with the other fats. There were no significant differences among the other fats in their effect on the plasma phospholipid level.