Dietary
sitostanol has a hypocholesterolemic effect because it decreases the absorption of
cholesterol. However, its effects on the
sitostanol concentrations in the blood and tissues are relatively unknown, especially in patients with
sitosterolemia and
xanthomatosis. These patients hyperabsorb all
sterols and fail to excrete ingested
sitosterol and other
plant sterols as normal people do. The goal of the present study was to examine the absorbability of dietary
sitostanol in humans and animals and its potential long-term effect. Two patients with
sitosterolemia were fed the
margarine Benecol (McNeill Nutritionals, Ft. Washington, PA), which is enriched in
sitostanol and
campestanol, for 7-18 wk. Their plasma
cholesterol levels decreased from 180 to 167 mg/dL and 153 to 113 mg/dL, respectively.
Campesterol and
sitosterol also decreased. However, their plasma
sitostanol levels increased from 1.6 to 10.1 mg/dL and from 2.8 to 7.9 mg/dL, respectively. Plasma
campestanol also increased. After
Benecol withdrawal, the decline in plasma of both
sitostanol and
campestanol was very sluggish. In an animal study, two groups of rats were fed high-
cholesterol diets with and without
sitostanol for 4 wk. As expected, plasma and liver
cholesterol levels decreased 18 and 53%, respectively. The
sitostanol in plasma increased fourfold, and
sitostanol increased threefold in skeletal muscle and twofold in heart muscle.
Campestanol also increased significantly in both plasma and tissues. Our data indicate that dietary
sitostanol and
campestanol are absorbed by patients with
sitosterolemia and
xanthomatosis and also by rats. The absorbed plant stanols were deposited in rat tissues. Once absorbed by sitosterolemic patients, the prolonged retention of
sitostanol and
campestanol in plasma might increase their atherogenic potential.