Selenium supplements may increase rather than reduce a person's risk of developing type 2 diabetes, research shows.
The University of Warwick study refutes the assumption from past trials that selenium tablets delay diabetes complications.
Scientists studied 1,202 people who did not have type 2 diabetes on entering the eight year Nutritional Prevention of Cancer trial.
During the trial, 58 people given selenium supplements and 39 given placebo tablets developed type 2 diabetes.
Participants who took the most selenium tablets had the highest risk of developing type 2 diabetes over the study period.
The scientists have concluded that selenium supplements may not prevent but in fact increase the risk of type 2 diabetes.
"At the moment we don't know what mechanims or mechanisms account for this finding," said lead study author Saverio Stranges at the University of Warwick.
"Our findings need to be replicated in larger clinical trials before conclusive evidence can be drawn on whether high doses of selenium supplements increase the risk of type 2 diabetes, as suggested by our study."