Dietary cholesterol contributes to the development and maintenance of hypercholesteremia in man. Intake of sitosterol prevents cholesterol resorption. This results in lowering of blood cholesterols to a basal endogenous level. Upon cessation of sitosterol intake hemocholesterols return to the original level. Excess supply of plant sterol was required in clinical experiments because the material used contained but 75 to 80 per cent of sitosterol and because of the large amount of endogenous cholesterol which has to be inactivated by the sitosterol, besides exogenous cholesterol.

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Cholesterol is absorbed by rabbits while its stereoisomer, sitosterol, is not resorbed. Cholesterol andl sitosterol form nonseparable crystals. W-hen the two sterols were fed simultaneously to rabbits, cholesterol wuas not absorbed, or was absorbed but partly. The degree of prevention of hypercholesteremia depended upon the amount of sitosterol fed with the cholesterol. A six-fold surplus of plant sterol was required in the experiments because the product employed contained but 75 to 80 per cent of sitosterol and because the supplied sitosterol binds not only exogenous cholesterol but also endogenous cholesterol present in the intestines. In the rabbit, prevention of hypercholesteremia, is tanitamount to prevention of atherosclerosis induced by cholesterol feeding.R ABBITS and other animal species fed cholesterol over a period of time develop hypercholesteremia which commonly leads to cholesterol atherosclerosis. Students of the steroid metabolism have long been impressed by reports on the inability of herbivorous and omnivorous animals to resorb phytosterol.Von Gierkel claimed that rabbits absorb phytosterol in the same manner as cholesterol, and Nikunil stated that mice can resorb phytosterol esters. Bondzyniski and Humnitzki3 and Dorre and Gardner4 identified equine fecal sterols as those of hay. Fraser and Gardner5 fed phytosterols to rabbits for from five to nine days: none were resorbed. Comparable series of rabbits, rats, mice, cats and a dog were fed by Schonheimer6 sitosterol, cholesterol, or neither sterol, respectively. Sitosterol was not resorbed by a single animal of these species. The identity of excreted sterols with the dietary sterols was proved by analysis of the feces. Yuasa7 found no increase in the cholesterol of portal vein blood of three dogs fed sitosterol. Sch6nheimer and coworkers8 failed to recover plant sterols in thoracic duct fluid of dogs fed peanut oil sterols. Schoenheimer9 also fed to dogs cholesFrom the Quincy City Hospital, Quincy, Mass., and the Kent General Hospital, Dover, Del.

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