Cholesterol Absorption and Synthesis in Vegetarians and Omnivores

SCOPE: Vegetarian diets are considered health-promoting; however, a plasma cholesterol lowering effect is not always observed. We investigate the link between vegetarian-diet-induced alterations in cholesterol metabolism. METHODS AND RESULTS: We study male and female omnivores, lacto-ovo vegetarians, lacto vegetarians, and vegans. Cholesterol intake, absorption, and fecal sterol excretion are measured as well as plasma concentrations of cholesterol and noncholesterol sterols. These serve as markers for cholesterol absorption, synthesis, and catabolism. The biliary cholesterol secretion rate is estimated. Flux data are related to body weight. Individual vegetarian diet groups are statistically compared to the omnivore group. Lacto vegetarians absorb 44% less dietary cholesterol, synthesized 22% more cholesterol, and show no differences in plasma total and LDL cholesterol. Vegan subjects absorb 90% less dietary cholesterol, synthesized 35% more cholesterol, and have a similar plasma total cholesterol, but a 13% lower plasma LDL cholesterol. No diet-related differences in biliary cholesterol secretion and absorption are observed. Total cholesterol absorption is lower only in vegans. Total cholesterol input is similar under all vegetarian diets. CONCLUSIONS: Unaltered biliary cholesterol secretion and higher cholesterol synthesis blunt the lowered dietary cholesterol intake in vegetarians. LDL cholesterol is significantly lower only in vegans.