Effect of dietary cholesterol and degree of fat unsaturation on plasma lipid levels, lipoprotein composition, and fecal steroid excretion in normal young adult men.

Effect of four test diets differing in the ratio of polyunsaturated to saturated fats (P/S, 1.8 vs 0.28) and two cholesterol levels (1,000 vs 300 mg/day) for each level of the P/S ratio was determined on plasma lipid levels, lipoprotein compositions and concentrations, and fecal steroid excretion in a controlled diet study with 11 normal young men using a crossover design. Plasma cholesterol levels were significantly decreased by the diets high in P/S ratio regardless of the dietary cholesterol levels (14% decrease by high cholesterol and 20% in low cholesterol) while the diets low in P/S ratio increased cholesterol by an average of 24 and 22% in presence of high and low cholesterol, respectively. Lipids and apoproteins of lower-density lipoproteins were changed in accordance with those of plasma cholesterol but changes in high-density lipoprotein (HDL) appear to depend on both cholesterol content and P/S ratio. Dietary cholesterol level profoundly influenced the excretion of neutral sterols and diets high in P/S ratio significantly (p less than 0.05) increased fecal bile acid extraction. The present study demonstrated that dietary polyunsaturated fats, when a moderate amount was consumed, were effective and beneficial hypocholesterolemic nutrients without reducing HDL-cholesterol.