Impact of selenium and cancer-prevention findings on the nutrition-health paradigm.

Evidence that selenium supplementation can reduce cancer risk is difficult to incorporate in nutrition thinking in which "nutritional essentiality" is the central concept. That concept, which defines nutrient need in terms of indispensability in diets and irreplaceable function in preventing specific deficiency disorders, was not developed to accommodate the function of a nutrient in reducing the risk to chronic disease, particularly when that function is not obligate but may be among several involved in maintaining good health. The findings of Clark et al. (JAMA 276, 1957-1963, 1996; Br J Urol 81, 730-734, 1998) suggest that selenium intakes of approximately twice the levels of the new Recommended Dietary Allowance or more can have such beneficial health effects. Because these intakes are above those required to support its accepted essential biochemical functions and because the maintenance of good general health as much as the prevention of specific deficiency disorders is the goal of public health, it is appropriate to reassess the nutritional essentiality paradigm. This discussion of the development and outcomes of the clinical intervention trials of Larry Clark and colleagues is presented in light of these issues.