Selenium may also protect us against cervical cancer. In 2015, 56 women with precancerous lesions received either 200 micrograms of selenium from yeast or a placebo every day for six months, in order to test this hypothesis. After the six months, 88% of the women given selenium had a regression of their lesions, compared to 56% in the placebo group. This difference came with a decrease in fasting blood sugar, insulin and insulin resistance, factors which are linked with cancer and metabolic issues.
However, not all forms of selenium have the same effects against cancer. The SELECT study, which gave 35,000 men either 200 micrograms of selenium (bound to the amino acid methionine), selenium and vitamin E, or a placebo, found no protective effect. This was seen as "proof" that selenium doesn't work because of its size and the publicity it generated. But as Life Extension describes, different types of selenium have different effects against cancer and other diseases. Sodium selenite can boost immunity, helping us fight tumour cells before they establish themselves. Selenium-methyl L-selenocysteine has shown an ability to kill cancer cells, even those which have lost the "suicide gene" that kills off damaged cells. Selenium from yeast provides antioxidant protection for cells and their DNA. Therefore, a supplement containing several types of selenium may be the best way to protect yourself against disease.