Effects of dietary fats and phytosterol on serum fatty acid composition and lipoprotein cholesterol in rats.

The effects of dietary fats and phytosterol on the fatty acid composition and lipoprotein cholesterol in serum were studied in female rats, with the following results. (1) The addition of 1% cholesterol to the 20% butter diet decreased the ratio of polyunsaturated fatty acid (PUFA) to saturated fatty acid (SFA) in serum. This phenomenon was negated when there was an intake of cod liver oil and wheat germ oil. (2) When cholesterol was added to the 20% butter diet, the serum total cholesterol increased 3.7-fold, due to an increase in the lower density lipoprotein (LDL + VLDL). (3) The addition of 5% phytosterol to the 10% butter-cholesterol diet reduced the total cholesterol level and increased the ratio of cholesterol in high density lipoprotein (HDL) to the cholesterol in LDL + VLDL. Although a 10% cod liver oil addition also reduced the total cholesterol level, the ratio of HDL/LDL + VLDL was similar to that of the 10% butter-cholesterol diet. (4) A direct relationship was found between the concentration of oleic acid (18:1) in serum and the total cholesterol level (r = 0.947) and also the level of LDL + VLDL-cholesterol (r = 0.935). These results show that cod liver oil, wheat germ oil, and phytosterol induce an increase in the PUFA/SFA ratio, promote hypocholesterolemia, and change lipoprotein concentration. However, there were indications that no relationship exists between the change in the total cholesterol level and the change in the ratio of HDL/LDL + VLDL, and that the increase of total cholesterol and LDL + VLDL-cholesterol was consistent with the increase of oleic acid in serum.