Re: Selenium and Vitamin E: Interesting Biology and Dashed Hope

Extract

The contrast between the highly optimistic results seen in the Nutritional Prevention of Cancer Trial (NPC Trial) (1) showing a 63% lower incidence of prostate cancer in individuals taking selenium and the negative result from the Selenium and Vitamin E Cancer Prevention Trial (SELECT) (2) has astonished many scientists. The contrast lead Klein (3) to conclude in his editorial that new scientific-based arguments are needed. The fact that selenium was ineffective in preventing prostate cancer in SELECT could be due to the type of selenium used. In SELECT, 200 μg of L-selenomethionine was chosen on the basis of weak scientific evidence, expert opinions, and voting, whereas in the NPC Trial, the 200 μg of high-selenium yeast contained only 20% of L-selenomethionine (ie, 40 μg). Other selenium-based compounds used in this trial supplement were selenocysteine, Se-methylselenocysteine, selenoethionine, selenoglutathione, selenodiglutathione, and selenite (representing another 40 μg) (4).

A meta-analysis of 20 epidemiological studies reported an inverse association between cancer and the plasma selenium levels for prostate cancer. All of these studies were based on the assessment of daily food intake and not on food supplements (5). Uptake of selenium from food and possibly also from high-selenium yeast differs from that of L-selenomethionine.