The safety evaluation of phytosterol esters. Part 6. The comparative absorption and tissue distribution of phytosterols in the rat

As part of an extensive safety evaluation programme, a series of studies ha s been conducted to determine the fate of phytosterols in the rat. Rats wer e dosed by oral gavage with C-14-labelled samples of cholesterol, beta-sito sterol or beta-sitostanol or H-3-labelled samples of beta-sitostanol, campe sterol, campestanol or stigmasterol dissolved in sunflower seed oil. Urine and faeces were collected for up to 96 hours after dosing. There was no qua ntification of biliary excreted material in these studies. Animals were sac rificed and either prepared for whole body autoradiography or tissues and c arcass remains were assayed for C-14 or H-3. The overall absorption of phyt osterols was low as judged by tissue and carcass levels of radioactivity. E limination from the body was mainly in the faeces and was initially very ra pid, but traces of material were still being excreted at 4 days after dosin g. While total absorption of the phytosterols could not be fully quantified without biliary excretion data, it was clear that cholesterol was absorbed to the greatest extent (27% of the dose in females at 24 hours). Campester ol (13%) was absorbed more than beta-sitosterol and stigmasterol (both 4%) which were absorbed more than beta-sitostanol and campestanol (1-2%). The a bsorption of phytosterols was slightly greater in females than males. For e ach test material, the overall pattern of tissue distribution of radioactiv ity was similar, with the adrenal glands, ovaries and intestinal epithelia shelving the highest levels and the longest retention of radioactivity. (C) 2000 Elsevier Science Ltd. All rights reserved.