Does Vitamin E Prevent or Promote Cancer?

It is difficult not to be confused by the research on vitamin E and cancer. Some studies say it causes cancer and others say it prevents cancer. The problem lies in the form of vitamin E used in the studies. Natural vitamin E consists of several tocopherols, with alpha-, gamma-, and delta- being the most abundant. Gamma-tocopherol is thought by many to be cancer preventative. When large doses of alpha-tocopherol are given, gamma-tocopherol is unable to be effective. An article published online in Cancer Prevention Research by Yang, et. al concluded that "Our recent results in animal models have demonstrated the cancer preventive activity of gamma- and delta-tocopherols as well as a naturally occurring mixture of tocopherols, and the lack of cancer preventive activity by alpha-tocopherol. Based on these results as well as information from the literature, we suggest that vitamin E, as ingested in the diet or in supplements that are rich in gamma-and delta-tocopherols, is cancer preventive; whereas supplementation with high doses of alpha-tocopherol is not."