Selenium deﬁciency is very rare in the United States and Canada, and selenium deﬁciency in isolation rarely causes overt illness. However, North Americans often have insufficient quantities of selenium.
Selenium nutritional status has recently been explained with the triage mechanism. The word “triage” means to sort and select. This term has been used on the battleﬁeld by military doctors to prioritize treatments for survival of the wounded. Similarly, the body selects means and ways, e.g. micronutrients and vitamins for an immediate need (survival) over the long-term needs by borrowing micronutrients from less critical depots in the body to use for emergency requirements.
To a large degree, the lack of dietary selenium is not clinically obvious, because this nutrient is prioritized to build essential selenoproteins at the expense of non-essential selenoproteins. However, a long-term insuﬃcient selenium status that prevents functioning of non-essential proteins may result in development of chronic degenerative conditions and ultimately shorten the life span and quality of life. The triage theory and insuﬃciency are particularly relevant to selenium status, since even modest low levels of selenium during the lifetime may increase risk of diseases of aging.