SELENIUM: TOXICOLOGICAL AND NUTRITIONAL ASPECTS FOR HUMANS

The overall objective of this project was to investigate the impact of ascorbic acid and/or methionine supplementation on selenium absorption and metabolism. These relationships might be of importance in determining either minimum selenium nutritional requirements or levels of intake at which this mineral becomes toxic. Three related studies compose the project. The first study involved the feeding of weanling mice. Rations varied in selenium, ascorbic acid, and methionine content. Supplementation with selenium resulted in decreased growth and increased selenium content of feces, liver tissue, and kidney tissue. Ascorbic acid supplementation in addition to selenium supplementation resulted in increased fecal selenium content and tended to decrease liver and kidney selenium content. Methionine supplementation with selenium also resulted in increased fecal selenium losses and decreased liver selenium content but tended to increase kidney tissue selenium content. In study II, nine young adult men and women were fed a laboratory-controlled diet with and without supplements of selenium or selenium plus ascorbic acid. Selenium supplementation resulted in increased selenium content of urine and feces. Concurrent ascorbic acid supplementation with selenium supplementation resulted in a small increase in fecal selenium loss which was insufficient to explain the dramatic decrease in urinary selenium excretion. In study III, a survey was conducted of food intakes of healthy adolescent boys and girls eating self-selected diets in relationship to blood serum and whole blood selenium content. Several other hematological and anthropometric parameters were measured. No relationships between dietary ascorbic acid or protein intakes and circulating selenium levels were found. Correlation coefficients suggested but did not prove that growth and/or sex as independent or related variables influenced blood serum and whole blood selenium levels