Selenium bioavailability from soybeans in rats fed a modified Torula yeast diet

Abstract

Selenium (Se) is an essential nutrient, and soy is a major plant source of dietary protein to humans. The United States produces one third of world's soybeans, and the Se‐rich Northern Plains states produce a large share of the Nation's soybeans. The present study examined the bioavailability of Se from a high‐protein cultivar we developed for Nebraska producers. Selenium fertilization was used during the seed development to produce high‐Se seeds to mimic those naturally produced. Male Sprague‐Dawley rats were depleted for Se after 56 days on a 30% Torula yeast diet (4.05 µg Se/kg) and repleted after 50 days on the same diet supplemented with 20, 30 and 40 µg Se/kg from the protein isolate or tofu (bean curd) prepared from that cultivar. The Se bioavailability was determined on the ability of Se from the test items to restore Se dependent enzyme glutathione peroxidase activity and tissue Se content in Se‐deficient rats compared with the standard responses in rats fed selenomethionine‐supplemented diets. Dietary supplementation with the protein isolate or tofu with 20, 30, and 40 µg Se/kg resulted in a dose‐dependent increase in glutathione peroxidase activity compared to rats fed the Se‐deficient diet. Similar increases were observed in the restoration of tissue Se. These dose‐dependent increases were comparable to that of selenomethionine. These results suggest that Se is bioavailable from this high‐protein cultivar and high‐Se soybeans may be a good source of dietary Se.