A US study suggested that genetic variations may be at play with vitamin E, increasing cancer risk in some individuals while decreasing risk for others. Multiple pathways may link the enzyme catechol-O-methyltransferase (COMT) to the vitamin E supplement, alpha-tocopherol, and cancer. The most extensively studied variant in COMT comes in three genetic forms: methionine/methionine, valine/methionine and valine/valine. The valine/valine variant is 3-4 times more enzymatically active than the methionine/methionine. In a random-effects meta-analysis of a trial of all female health care professionals in good health at the beginning, which lasted 10 years with 10 years post-trial follow-up, in the overall period, for women with the methionine/methionine variant who took vitamin E compared to placebo, rates of total cancer were 12% significantly lower, while they were 18% higher for women with the valine/valine variant who took vitamin E compared to placebo. The results have been validated in another trial which included only male smokers from Finland. The investigators previously found that genetic differences in COMT modified the effects of vitamin E on cardiovascular disease risk. The findings indicate that genetic variation as a determinant of the benefits and even harms of supplements, like alpha-tocopherol, used for health promotion. Source: https://academic.oup.com/
