Effect of dietary brussels sprouts with increased selenium content on mammary carcinogenesis in the rat

Brussels sprouts (Brassica oleracea, L; Jade cross E, hybrid cultivar) were cultivated with inorganic selenium added to the plant growth medium. Sprague-Dawley, female, weanling rats were divided into groups and fed 20% brussels sprouts diets containing either 0.03, 0.58, 1.29, or 6.71 ppm of selenium naturally occurring in the sprouts. These diets were fed 2 weeks before and 2 weeks after a single dose of 7,12-dimethylbenz[a]anthracene (DMBA), and the rats were then placed on a low selenium basal diet for an additional 25 weeks. All brussels sprouts diets reduced the incidence of DMBA-induced mammary carcinogenesis. Increased dietary levels of naturally occurring selenium did not further depress mammary tumorigenesis. The time periods of selenium feeding may have been too brief to observe any additional tumor reductions.