Dependence of the effects of dietary cholesterol and experimental conditions on serum lipids in man II. Effects of dietary cholesterol in a linoleic acid-poor diet

Abstract

In this experiment the effect of dietary cholesterol on serum cholesterol levels was tested in a linoleic acid-poor diet. In a cross-over design 34 healthy students received a linoleic acid-poor diet for 6 weeks at two levels of dietary cholesterol for 3 weeks each. The visible fat was supplied in the form of margarine so that the diet contained only 5 energy% linoleic acid. The high-cholesterol diet was obtained by providing two egg yolks a day. During the experimental period an intestinal infection was noticed, based on their diaries, in 16 subjects. Because of the expected influence on serum cholesterol levels all suspected individuals were removed from the records by independent experts and treated separately. Only the results of the 18 healthy persons are discussed in this paper. Supplementation of two eggs a day caused a highly significant (P < 0.01) rise in serum cholesterol levels of 26 ± 20 mg/100 ml (0.65 mmole/liter) in the two experimental groups. After correction for differences in the fat content of the diets an effect of 21 mg (0.54 mmole/liter) remained. As noticed in the first experiment (part 1) the rise in serum cholesterol levels in groups fed a high-cholesterol, high-polyunsaturated fat diet was only 11 mg/100 ml (0.29 mmole/liter). Comparing the two results it is concluded that the effect of dietary cholesterol is clearly dependent on the type of fat present in the diet. Eggs will have a rather important elevating effect in a saturated fat diet, which is the more deleterious as the saturated fat already induces high cholesterol levels. However, linoleic acid-rich fat reduces serum cholesterol levels markedly, while the opposing effect of dietary cholesterol in this case is much smaller. The results of this study emphasize the importance of considering the complexity and interrelations of all constituents of a diet in affecting health parameters. By substituting the type of fat and changing the amount of egg cholesterol, it seems feasible to influence serum cholesterol levels of young healthy men in the range of 145 to 210 mg/100 ml (3.7 to 5.4 mmole/liter).