Positive Health Online

Abstract

Finley, Davis and Feng, US Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58203-9034, USA investigated the effect of selenium on rats with colon cancer .

Background

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 demonstrated the efficacy of selenium (Se) for prevention of colon cancer in humans. The metabolism of Se depends on its chemical form, and studies have shown that the chemical form of Se in broccoli does not accumulate in the body as fast as other forms of Se and may be especially beneficial for prevention of cancer.

Methodology

Two experiments were conducted. In the first, Fisher F-344 rats (n=45) were allotted randomly to torula yeast-based diets supplemented with the following: 1) no Se; 2) 0.1 ug Se/g diet as selenate; 3) 1.0 ug Se/g diet as selenate; 4) 0.1 ug Se/g diet as selenized broccoli (Se concentration of approximately 500 ug/g); or 5) 1.0 ug Se/g diet as selenized broccoli. In Experiment 2, rats (n=80) were allotted randomly to the same basal diet supplemented with the following: 1) no added Se; 2) 2.0 ug Se/g diet as selenite; 3) 2.0 ug Se/g diet as selenite + low Se broccoli; and 4) 2.0 ug Se/g diet as selenized broccoli. Rats were fed the diets for 2 weeks and injected with a chemical carcinogen (3,2 dimethyl 4-amino biphenyl or dimethyl-hydrazine in Experiment 1 or dimethyl hydrazine in Experiment 2; two rats/treatment were used as vehicle controls).

Results

Supranutritional amounts of Se supplied as high Se broccoli significantly decreased the incidence of aberrant crypts (AC) and aberrant crypt foci (ACF; preneoplastic lesions indicative of colon cancer) compared with other dietary treatments. Diets were 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.

Conclusion

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 .

References

Finley JW et al. Selenium from high selenium broccoli protects rats from colon cancer. The Journal of Nutrition 130 (9): 2384-9. Sep 2000.