At present, no-one knows if taking selenium supplements can reduce your risk of developing cancer. But, there is a lot of interest and research looking into this.

A few years ago an American study looked at whether people could reduce their risk of developing non-melanoma skin cancer by taking selenium supplements for at least five years. People taking part took either a yeast tablet with selenium or a yeast tablet with no selenium.

After six and a half years it was found that taking selenium didn't help to prevent skin cancer from developing. But, fewer people died of cancer in the group taking selenium than in the group not taking it. People taking selenium also developed fewer cancers of the lung, bowel and prostate than people in the other group.

Because of this finding several studies have looked at whether selenium can help to prevent various cancers. But, the results have been conflicting so it's still not clear if selenium can help to reduce cancer.

The results of some studies have suggested that people who have recently stopped smoking and people with low levels of selenium may be more likely to benefit from taking selenium supplements. But, further research is needed.

Many scientists agree that the evidence for selenium reducing cancer risk is most promising for prostate cancer. A large study called the SELECT trial is going on in the USA to try to answer this. Over thirty thousand men are taking part. They have been taking selenium and Vitamin E supplements for several years to see if this will help to prevent prostate cancer. The results should be available in 2012.

If you want to make sure you are taking enough selenium in your diet eating a range of foods including fish, such as cod and salmon, chicken, turkey and brazil nuts will help. Or, if you feel you would like to try taking selenium supplements, the Food Standards Agency say that taking up to 350 micrograms per day is unlikely to do any harm but higher doses can cause unpleasant side effects.

References

• Clark, LC et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomised controlled trial. JAMA 1996;276:1957-63.
• Klein et al. SELECT: the selenium and Vitamin E prevention trial. Urological Oncology 2003