The new systematic review published by The Cochrane Library analysed data from 12 trials involving almost 20,000 people, finding that supplementation with selenium is not effective in the prevention of cardiovascular disease (CVD).
Led by Dr Karen Rees from the University of Warwick, UK, the research group explained that in recent years the use of selenium enriched foods, supplements and fertilizers has increased in many countries because of the perception that selenium may reduce the risk of cardiovascular disease and other chronic conditions.
“Therefore, it is important to understand the effects of a nutrient that is frequently supplemented on common conditions such as cardiovascular disease or diabetes,” they explained. “This review assessed the effects of providing selenium supplements to healthy adults in order to prevent the occurrence of cardiovascular disease.”
Rees and her team found that for well-nourished adults, currently available evidence does not support selenium for preventing heart disease when compared against placebo:
"The limited evidence available at this time does not support the use of selenium supplements in the primary prevention of heart disease in well-nourished populations," said co-researcher Saverio Stranges, also from the University of Warwick.
"Taking selenium supplements is probably neither beneficial nor harmful, but given the lack of trials to date, we cannot rule out some low level of increased risk of type 2 diabetes, at least in individuals with high selenium status," he said.
‘Limited’ evidence
Rees and her team analysed the findings of 12 placebo controlled randomised double-blinded trials to measure the effects of selenium supplementation on heart disease risk. From these 12 trials, the team pooled data from 19,715 healthy adults who had been randomly assigned to receive either selenium supplements or placebo.
They noted that the vast majority of participants involved in these trials were male individuals from the US – where people are already well nourished and take large amounts of selenium from natural foods.
“In our review, providing selenium supplements to healthy adults did not prevent the occurrence of major cardiovascular disease,” they confirmed, adding that an increased risk of developing type 2 diabetes when taking selenium supplements – as suggested in some previous studies – could not definitely be ruled out in the review.
The authors noted that selenium is commonly added to several multivitamin and mineral preparations and enriched foods that are widely used by the general public in many Western countries.
However, the results of their review, based on a small number of available clinical trials, “do not support a role for selenium supplementation in the primary prevention of CVD at the present time, especially in those individuals and populations with adequate-to-high selenium status.”
“This review of the available evidence to date suggests that taking selenium supplements is neither beneficial nor harmful for cardiovascular disease, but it is probably unnecessary for those who are already well nourished and who take large amounts of selenium from natural foods,” concluded Rees and her team.
"We need to know what effect selenium supplements have in less well-nourished populations where dietary intake of the element is lower," said Stranges.
"However, the indiscriminate and widespread use of selenium supplements in individuals and populations with adequate or high selenium status is not justified and should not be encouraged,” he said.
Source: The Cochrane Library
Published online 31 January 2013, doi: 10.1002/14651858.CD009671.pub2
“Selenium supplementation for the primary prevention of cardiovascular disease”
Authors: Karen Rees, Louise Hartley, Camilla Day, Nadine Flowers, Aileen Clarke, Saverio Stranges