Dr Saverio Stranges said although high selenium levels were not exclusively caused by people taking dietary supplements, the results of the study were concerning because the use of selenium dietary supplements had risen considerably in the UK in recent years. He said this was largely due to the perception that selenium can reduce the risk of cancer and other diseases.

He said: "This use has spread despite a lack of definitive evidence on selenium supplements efficacy for cancer and other chronic disease prevention.  The cholesterol increases we have identified may have important implications for public health. In fact, such a difference could translate into a large number of premature deaths from coronary heart disease.

"We believe that the widespread use of selenium supplements, or of any other strategy that artificially increases selenium status above the level required is unwarranted at the present time. Further research is needed to examine the full range of health effects of increased selenium, whether beneficial or detrimental."

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