Optimal Selenium Intake Wards Off Diseases

OAKLAND, Calif.Maintaining adequate dietary levels of selenium may help prevent age-related conditions such as immune dysfunction, cardiovascular disease and cancer, according to a new analysis from the Childrens Hospital Oakland Research Institute (CHORI).

The analysis, conducted by CHORI Associate Staff Scientist Joyce McCann, PhD, and Senior Scientist Bruce Ames, PhD, was designed to test Ames triage" theory that provides a new basis for determining the optimum intake of individual vitamins and minerals by measuring long-term insidious damage associated with aging. The analysis provides a consistent scientific basis for establishing optimum vitamin and mineral intakes, which will add credence to recommendations for improving inadequacies in micronutrient intake of the American diet.

The triage theory explains why diseases associated with aging may be unintended consequences of mechanisms developed during evolution to protect metabolic processes against episodic vitamin and mineral shortages. Ames reasoned these mechanisms are focused on preserving vitamin and mineral-dependent functions required for animals to survive for reproduction, at the expense of other functions required to sustain long-term healthnot a priority for evolution. Ames proposed that modest shortages in vitamin and mineral lead to insidious metabolic damage in so-called less critical functions" that over time accelerates aging and may lead to diseases of aging such as cancer, heart disease and dementia. If correct, the triage theory has widespread implications for public health because modest vitamin and mineral deficiencies are quite common. It also suggests a new scientifically based and consistent strategy for establishing optimal vitamin and mineral intake standards, and it provides a research strategy to uncover early biomarkers of chronic disease.

This selenium analysis is the second in a series of literature-based studies conducted by McCann and Ames to test the basic premises of the triage theory by constructing triage-based biological profiles of individual vitamin and minerals.

The new analysis reviews about half of the 25 known mammalian selenoproteins; all of those with mouse knockout or human mutant phenotypes that could be used as criteria for a classification of essential" or nonessential." On modest selenium deficiency, nonessential selenoprotein activities and concentrations are preferentially lost. Mechanisms include the requirement of a special form of tRNA sensitive to selenium deficiency for translation of nonessential selenoprotein mRNAs. The same set of age-related diseases and conditions, including cancer, heart disease and immune dysfunction, are prospectively associated with modest selenium deficiency and also with genetic dysfunction of nonessential selenoproteins, suggesting that selenium deficiency could be a causal factor, a possibility strengthened by mechanistic evidence. Modest selenium deficiency is common in many parts of the world; optimal intake could prevent future disease.