Absorption, metabolism, and serum concentrations of cholesterol in vegetarians: effects of cholesterol feeding.

Serum concentrations and metabolism of cholesterol were studied in vegetarians basally and during a dietary cholesterol load. Cholesterol absorption efficiency was normal and synthesis was slightly enhanced, even though serum cholesterol precursors were not increased. The serum concentrations of total and low-density-lipoprotein cholesterol were decreased proportionally to the reduced intake and absolute absorption of cholesterol. Fecal plant sterols were negatively correlated with the absorption efficiency of cholesterol and positively with fecal sterols and cholesterol synthesis, suggesting interference of high plant sterol intakes with cholesterol absorption. Cholesterol saturation and bile acid composition of the bile were not changed. The increased serum plant sterol-cholesterol ratios were positively related to the intake and negatively to the biliary secretion of plant sterols. Cholesterol feeding increased absolute cholesterol absorption and serum concentrations of total and low-density-lipoprotein cholesterol, did not change absorption efficiency or synthesis of cholesterol, but increased fecal cholestanol excretion.