Submitted to: Biofactors
Publication Type: Proceedings
Publication Acceptance Date: February 21, 2001
Publication Date: N/A
Interpretive Summary: Because of its reported health benefits, many people are seeking to increase their intake of the essential nutrient selenium (Se). The position of many dietary professionals is that whenever possible people should obtain their nutrients through their diet. Little work has been done on the relative health benefits of food forms of Se. This is complicated by the observation that similar foods may be either high or low in Se depending on the geographical location where they are produced. We have tested the biological benefits of Se from high-Se broccoli and high-Se wheat. High-Se broccoli was relatively ineffective for increasing tissue Se concentrations or increasing the activity of proteins that use Se, whereas high-Se wheat was quite effective for increasing tissue Se concentrations and activities of Se-requiring proteins. Selenium from high-Se broccoli markedly lowered the risk of colon cancer in rats. High- Se wheat also was effective for decreasing colon carcinogenesis in rats, but the decrease was not as marked as for high-Se broccoli. These results demonstrate that foods containing high amounts of Se may result in different biological actions and that foods that do not increase tissue Se concentrations or selenium enzyme activities may actually be superior forms of Se for inhibiting colon cancer.
Technical Abstract: The reduction in incidence of chemically-induced colon cancer by foods high in selenium (Se) was investigated in Fisher-344 rats. The foods used were high-Se broccoli (produced in a greenhouse by addition of selenate to the media surrounding the plant roots) and a processed high-Se wheat product (made by milling high-Se wheat purchased from a seleniferous area). Weanling rats were fed diets containing different amounts of Se from these foods or from selenium salts (selenite and selenate). Early in the experiment the animals were injected with a chemical carcinogen. After 11 weeks on diets animals were killed and the colons examined for preneoplastic lesions (aberrant crypts foci, ACF). ACF were significantly reduced in animals fed supra-nutritional amounts of Se from broccoli, despite the finding that Se from broccoli was poorly bioavailable. Supra- nutritional amounts of Se from high-Se processed wheat also significantly reduced aberrant crypts (AC), although pure selenomethionine, (the predominant chemical form of Se in wheat), did not significantly reduce AC. These results emphasize the need to study Se in food forms, and not extrapolate from previous studies using pure chemical forms in cancer inhibition studies. They also demonstrate that foods with high Se bioavailability are not necessarily the most efficacious for cancer incidence reduction.