The Epidemiology of Selenium and Human Health

Health risk assessment of environmental selenium: Emerging evidence and challenges

“…In addition, the scientific literature encompasses a large number of nutritional epidemiology studies on the long-term health effects of selenium carried out in populations living in non-seleniferous regions and countries. These studies include experimental investigations (randomized controlled trials) and observational studies, the latter characterized by case-control, cohort, cross-sectional and ecologic design and being characterized by a far weaker ability compared with trials in addressing the selenium and health relation ( 1 , 14 , 15 ). While the entire review of this huge literature goes beyond the possibility of this report, we aim at briefly updating the evidence generated by the most recent environmental and nutritional studies on the human health effects of selenium, the biological plausibility of this relation, an overview of the challenges that these studies and their interpretation pose, and finally their implications on the adequacy of current environmental selenium standards.…”

“…Several studies have investigated the effects on human health of even limited changes in exposure to environmental selenium, which occurs through different environmental sources (primarily diet, but also air pollution, occupational environment, smoking and drinking water), in populations characterized by exposure levels not considered a priori to be unusually ‘low’ or ‘high’ ( 14 ). These studies, generally carried out in Western populations, have investigated a broad number of health outcomes, but in the majority of cases they focused on cancer risk ( 14 , 15 ). However, most of these studies had an observational design, thus suffering from the potential severe bias due to unmeasured confounding and exposure misclassification even in prospective cohort studies, in addition to the other biases typically effecting studies with case-control, cross-sectional and clearly ecologic design ( 1 , 14 , 29 ).…”

Selenium, selenoprotein P, and Alzheimer's disease: is there a link?

“…Although a number of human studies have addressed the possible role of Se supplementation in preventing cognitive decline or AD, the data are still inconclusive. The reason for inconsistencies between different studies may be related to confounding bias, differences in evaluation of dementia and cognitive performance, inadequate controls, unspecified initial Se status and speciation, so only a fraction of the studies may be described as 'high quality' [34,158].…”

“…In our opinion, further studies should more directly address the issue of optimal Se supply, relevant biomarkers of Se status and optimal reference ranges [126]. For instance, some authors consider plasma/serum or nail Se as mainly Se exposure markers, not reflecting the body's selenoprotein machinery and Se speciation in general [158]. Aside from purely analytical complications related to the measurement itself, the activity or concentration of SELENOP and GPX3 are also being questioned as relevant markers, since in this case the terms 'optimal' or 'optimized' expression/activity [164] is often substituted by 'maximal' or 'maximized' [163], which is probably not appropriate for all populations and health conditions.…”

Toenail selenium as an indicator of environmental exposure: A cross-sectional study

“…Selenium (Se) is a metalloid showing an intriguing relation with human health, particularly with cancer (1,2) and with other diseases (3,4). The main source of Se exposure is the dietary intake, closely linked to Se content in soil.…”