Dual role of selenium in health and disease

Marco Vinceti, Tommaso Filippini, Lauren A Wise

Oral presentation at 1 16th International Symposium on Trace Elements in Man and Animals (TEMA-16), ISTERH 2017 and NTES 2017 meeting

Saint-Petersburg, Russia at 26-29 June, 2017.

The relation between an adequate selenium intake and human health has received a large interest in the most recent years, with reference to the etiology and prevention of chronic disease such as cancer and cardiovascular disease as well as other clinical endpoints. However, the role of this element in the etiopathogenesis of human diseases is still far from being entirely elucidated, and it appears to have a Janus-faced nature. In fact, this element was suggested to decrease cancer risk following the results of several observational studies and a randomized trial, but the most recent trials have shown no activity and even adverse effects of selenium administration on cancer risk. Selenium has also been claimed to exert beneficial effect on risk of diabetes and more generally metabolic diseases, but again the recent randomized trials have shown an opposite effect, i.e. an increased risk of diabetes following selenium supplementation. Cardiovascular risk has not been decreased by selenium supplementation, which exerted instead a beneficial effect on the incidence of a severe cardiomyopathy named ‘Keshan disease’. Keshan disease has been described in low-selenium areas of China, and it mainly affects children and women of childbearing age. Recent epidemiologic studies also suggested a role of selenium in the etiology of neurological disease, with some indications of an adverse effect induced by inorganic selenium.

This dual, intriguing and paradoxical activity of selenium on human health shown or suggested by epidemiologic studies is mirrored by laboratory studies, which have shown both the antioxidant activity of selenium-containing proteins and a pro-oxidant activity of the element, as well as conflicting activities of selenium and selenoproteins on carcinogenesis.

The recent evidence yielded by epidemiologic and laboratory studies on the effects of selenium on human health needs therefore to be carefully considered for a new risk assessment of selenium, with reference to both its deficiency and excess. More adequate standards of selenium exposure also need to be set, taking into account the different biological, nutritional and toxicological activities of the various chemical forms of this element.