In 1996, Clark et al1 published the results from a double-blind placebo-controlled trial investigating the role of selenium supplements in cancer. In the study, 1312 subjects with a history of non-melanoma skin cancer were randomised to receive either 200 µg per day selenium yeast or a placebo. When the authors analysed the results they found that selenium had no significant effect on non-melanoma skin cancer rates. However, the group being administered the 200 µg per day selenium a had 50 % lower total mortality from cancer, a 37 % lower total cancer incidence, 63 % fewer cases of prostate cancer, 58 % fewer cases of colon cancer and 46 % fewer cases of lung cancer. Those subjects who experienced the greatest benefit from the selenium supplements were the ones in the lowest tertile for plasma selenium (<106 µg/L). Supplementation of this lowest tertile resulted in a 48 % reduction in the risk of cancer.