Interrelations Between the Kind and Amount of Dietary Fat and Dietary Cholesterol in Experimental Hypercholesterolemia

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Abstract
An extremely large number of variables are reported to influence hypercholesterolemia and atherosclerosis in experimental studies, and there is need for experimental designs adequate to evaluate the relative importance of these variables and their interrelation to each other. A study is reported in which five different oils, each at three levels, and two different levels of dietary cholesterol were investigated. Only two animals per groups were used. All of the major variables (time, kinds of oil, level of oil, and amount of dietary cholesterol) have significant effects upon the hypercholesterolemia and many of the numerous interactions are also significant. It would appear, therefore, that the action of any of these variables can only be stated at the present time in terms relative to the others. The same situation is probably true with other variables not specifically included in this study. Such interrelations may well account for the apparently contradictory results in the literature as to the effects of various fats upon hypercholesterolemia in human subjects. Regression equations relating the amount of fatty acid (saturated, monounsaturated, and polyunsaturated) in the diet to the serum cholesterol level were calculated. With these three variables in the equation, the coefficient for the monounsaturated acid is positive. The coefficients for the saturated and polyunsaturated acids are negative. The equation suggests that the monounsaturated acid raises the serum cholesterol level while the saturated and polyunsaturated acids reduce it, the saturated acids being about one-fourth as active as the polyunsaturated acid. However, other equations can be derived which give as good a “fit” as this equation, and the magnitude and even the sign of the coefficients vary depending upon the variables included in the equation. Caution should be used in assigning too much significance to the calculated coefficients.