Lymphatic absorption of shellfish sterols and their effects on cholesterol absorption.

Studies have been conducted on the absorbability of individual sterols from a mixture of oyster sterols when administered intragastrically to rats with indwelling catheters in the left thoracic duct. In addition, the effect of oyster sterols on cholesterol absorption has been assessed using [4-14C] cholesterol in the mixture, and comparison against absorption of cholesterol alone. The order of absorbability (percentage absorption) of individual sterols from the mixture of oyster sterols was: cholesterol greater than or equal to 26-carbon sterols greater than or equal to dehydrocholesterol greater than 24-methylene cholesterol greater than brassicasterol greater than plant sterols. The absorption of noncholesterol sterols was 8.2 +/- 0.8% of the fed dose, or less than half of that for an equivalent level of cholesterol alone. The presence of these sterols in mixtures containing cholesterol reduced lymphatic absorption of cholesterol by 25 to 40% compared to absorption of the same amount of cholesterol administered alone, or to an amount of cholesterol equal to the total oyster sterols, respectively. These studies suggest that shellfish sterols are poorly absorbed, and, like plant sterols, effectively reduce dietary and/or endogenous cholesterol absorption from the intestine.