Low density and high density lipoprotein kinetics and sterol balance in vegetarians.

Vegetarians have lower than average plasma lipid levels. Possible mechanisms were studied by measuring the kinetics of LDL-B protein and HDL-AI protein in 7 young male vegetarians and 6 omnivorous control subjects; sterol balances were also determined in a further study with the 6 additional control subjects whose intake of cholesterol was low. Plasma total cholesterol, LDL cholesterol and LDL-B protein were significantly lower in the vegetarians and plasma AI protein concentrations also tended to be lower. The flux or production of LDL was significantly lower, 9.1 +/- 2.3 mg/kg/d (mean +/- SD) compared to 11.8 +/- 0.6 mg/kg/d in the controls and appeared to explain the low levels of LDL. The fractional removal rate of HDL-AI protein was significantly greater in the vegetarians (0.043 +/- 0.011 versus 0.027 +/- 0.011 for the fractions of pool 1 cleared per hour) and appeared to account for the low plasma AI levels. In the second study, bile acid excretion was significantly lower in the vegetarians and estimated cholesterol synthesis was in the low normal range. Low rates of LDL-B protein formation have been reported in other subjects with low LDL cholesterol concentrations and in the vegetarians presumably reflect the composite of several dietary factors.