The absorption of α-tocopherol in man

Abstract

1. Physiological oral doses of DL [5-Me-3H]α-tocopherol were administered to fasting subjects with various disease states, with and without steatorrhoea, and net absorption was calculated by measurement of faecal unabsorbed radioactivity. In each subject studied more than 70% of the faecal radioactivity was excreted as unchanged α-tocopherol.2. α-Tocopherol absorption was significantly less in subjects with steatorrhoea (mean 59.4%, range 31–83%) than in those without steatorrhoea (mean 72.4%, range 51–86%). Nineteen out of twenty-four subjects with steatorrhoea absorbed less than 65% of the α-tocopherol dose, while twenty-two out of twenty-six subjects without steatorrhoea absorbed more than 65%. There was a significant correlation between the severity of steatorrhoea and α-tocopherol absorption. In a wide range of diseases steatorrhoea appeared to be the common factor associated with a decrease in α-tocopherol absorption; however, in subjects after gastric surgery α-tocopherol absorption was often low even in the absence of steatorrhoea, and this may be an important factor in explaining the high incidence of vitamin E deficiency in such patients.3. Radioactivity in the plasma was maximal 6–12 h after dosing. Plasma radioactivity curves were significantly lower in patients with steatorrhoea than in those without steatorrhoea, but there was considerable overlap. In some patients with severe deficiency and severe steatorrhoea there was no detectable plasma response even with considerable absorption of up to 40% of the administered dose. Three patients with severe dietary deficiency of the vitamin and no steatorrhoea also showed a decreased plasma radioactivity.4. Three subjects were studied twice, initially when deficient in α-tocopherol and a second time after repletion with α-tocopherol acetate. There was no evidence for a compensatory mechanism to increase α-tocopherol absorption in α-tocopherol deficiency.5. A small quantity of the administered dose (almost always less than 6%) was excreted in the urine.