Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 4, 2000
Publication Date: N/A
Interpretive Summary: Numerous studies have shown that selenium supplementation in amounts greater than the dietary requirement is protective against several cancers, including colon cancer. Previous research has also shown that the amount of protection against cancer that is afforded by Se is dependent on the chemical form of the selenium. We have previously demonstrated that selenium in high-selenium broccoli is in a unique form and is uniquely metabolized. Also, selenium from high-selenium broccoli does not accumulate in the body as fast as selenium from other sources; this suggests that there is less danger of selenium toxicity. In this study, we have demonstrated that selenium from broccoli is more protective against colon cancer than salt forms of selenium. Salt forms of selenium, when compared to a control group, did not reduce the number of lesions indicative of colon cancer in the colons of rats, but selenium from high- selenium broccoli reduced the number of cancerous lesions by 1/3 to 1/2. These results, combined with the results of previous studies, suggest that broccoli may be a source of supplemental selenium that provides superior protection against cancer with less of a risk for toxic accumulation within the body.
Technical Abstract: Colon cancer is the third most common newly diagnosed cancer in the United States and the third most common cause of cancer-related deaths. Previous supplementation studies have established the efficacy of selenium (Se) for prevention of colon cancer in humans. It is well established that the metabolism of Se depends on its chemical form, and studies have suggested that Se in broccoli is in a chemical form that does not accumulate in the body as fast as other forms of Se, and may be especially beneficial for prevention of cancer. In the present study, Fisher F-344 rats were fed diets containing adequate (0.1 ug Se/g diet) or supranutritional amounts of Se (1.0 or 2.0 ug Se/g diet) provided as selenate, selenite or high-Se broccoli, and injected with a chemical carcinogen (3,2 dimethyl 4-amino biphenyl or dimethyl-hydrazine). Supranutritional amounts of Se supplied as high-Se broccoli significantly decreased (P<0.05) the incidence of aberrant crypts (AC) and aberrant crypt foci (ACF; pre-neoplastic lesions indicative of colon cancer) as compared to other dietary treatments. Diets controlled for the presence or absence of broccoli and for the total amount of Se. The reduction in AC and ACF was a function of Se in high-Se broccoli and not a result of broccoli alone or Se alone. Adequate dietary Se supplied as high-Se broccoli did not accumulate in tissues or increase glutathione peroxidase activity as well as other forms and amounts of Se. Thus, Se from high-Se broccoli may be metabolized in a manner that diverts much of the Se into a pool that provides protection against colon cancer.