Regulation of cholesterol metabolism by dietary protein and n-6 polyunsaturated fatty acids.

The modulating processes of dietary vegetable protein and polyunsaturated fatty acids (PUFAs) on cholesterol (CH) metabolism are very complicated. Since dietary protein can affect PUFA absorption and synthesis through the effects of its amino acid components, the CH-lowering of PUFAs may be modulated by dietary proteins. The effect of dietary PUFAs on the CH-lowering mechanism of vegetable proteins is mainly additive and complementary, but not competitive. Dietary vegetable protein reduces intestinal CH absorption, enhances catabolism of the CH-carrying lipoproteins, increases the LDL receptor activity, and modulates CH metabolic enzymes through the amino acid-modulated action of hormones. PUFAs may modulate CH metabolism through the action of eicosanoids which modulates the activity of the enzymes responsible for CH metabolism.