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United States Department of Agriculture

Agricultural Research Service

Title: Current Evidence and Research Needs to Support a Health Claim for Selenium and Cancer Prevention

Author
item Combs, Gerald

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 2, 2004
Publication Date: January 31, 2005
Repository URL: http://handle.nal.usda.gov/10113/1957
Citation: Combs, G.F. 2005. Current evidence and research needs to support a health claim for selenium and cancer prevention. Journal of Nutrition. 135:343-347.

Interpretive Summary: Selenium is an essential nutrient that has been shown to be anti-carcinogenic in a variety of animal tumor models and cancer preventive in several human clinical trials as well as some, but not all epidemiological observations. It has been consistently found that both inorganic and organic Se-compounds, including those in foods, can be anti-tumorigenic when consumed at doses greater than those required to support the maximal expression of the known selenium-containing enzymes that are thought responsible for the nutritional effects of the element. Thus, the plausibility of Se as a cancer-protective factor is clear; still, research is needed to support evidence-based evaluation of this hypothesis. This includes well planned clinical trials, analytical tools for speciating Se in foods and tissues; better means of assessing Se status in ways that are relevant to cancer prevention, clarification of the roles of selenoenzymes in carcinogenesis; elucidation of the role of Se in promoting healthful hindgut microflora; and determination of the minimal dose of Se that is both safe and effective in reducing cancer risk.

Technical Abstract: Selenium was recognized as a nutritional essential only in the late 1950's. That it might also be anti-carcinogenic was first suggested a decade later based on ecological relationships of cancer mortality rates and forage crop Se contents in the United States. Since that time, a substantial body of scientific evidence indicates that Se can, indeed, play a role in cancer prevention. This is supported by a remarkably consistent body of findings from studies with animal tumor and cell culture models, and by some, but not all epidemiological observations. The body of clinical trial data is less extensive, yet also supportive. The consistent findings from this evidence are that both inorganic and organic Se-compounds can be anti-tumorgenic at doses greater than those required to support the maximal expression of the selenoenzymes which are generally regarded as discharging the nutritional effects of the element. Thus, these anti-carcinogenic doses have been called 'supranutritional'. While the plausibility of Se as a cancer-protective factor is clear, other research is needed to support evidence-based evaluation of this hypothesis. In addition to further, well planned clinical trials, that research includes the development of analytical tools for speciating Se in foods and biological tissues; the development of better means of assessing Se status in ways that are relevant to cancer prevention; the clarification of the roles, if any, of selenoenzymes in carcinogenesis; the elucidation of the role of Se in promoting healthful hindgut microflora; and the determination of the minimal dose of Se that is both safe and effective in reducing cancer risk.

Last Modified: 4/24/2014
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