Absorption and transport of shellfish sterols in human subjects.

While individually cholesterol is the most abundant sterol in clams, oysters, and scallops, five different major noncholesterol sterols (a C-26 sterol, 22-dehydrocholesterol, brassicasterol, 24-methylene cholesterol, and a C-29 sterol) comprise some 60% of the total sterols, a situation unique among foods of animal origin that humans consume. In order to measure the intestinal absorption and transport of these noncholesterol shellfish sterols by humans, clams, oysters, and scallops were fed daily for 3-4 wk to 9 subjects and in a single meal to 8 subjects. The major shellfish sterols in the diet and in the plasma, individual plasma lipoproteins, red blood cells, and feces were analyzed by digitonin precipitation, thin-layer and gas-liquid chromatography-mass spectrometry. The absorption of these shellfish sterols was ascertained both by their appearance in the blood of the subjects fed shellfish and by their intake and output in the feces. After daily feeding for 3--4 wk, shellfish sterols were identified for the first time in the plasma lipids, in lipoproteins (chiefly in low-density lipoprotein), and in red blood cells of all subjects. The absorption of the dietary C-26 sterol, 22-dehydrocholesterol, brassicasterol, 24-methylene cholesterol was 54%, 35%, 4% and 11%, respectively. Our data indicated that the intestinal mucosa of humans absorbs these unusual sterols, and then they enter into the tissues and overall sterol metabolism of the body.