The recent Medical Letter article on vitamin supplements1 included 2 sentences on vitamin E that could be misleading. "Vitamin E in food, which is mostly gamma-tocopherol, acts as an antioxidant. Vitamin E in supplements is mostly alpha-tocopherol, which may block the anti-oxidant effect of gamma-tocopherol and may have a pro-oxidant effect in vivo."

Gamma-tocopherol is the most common form of vitamin E in the North American diet, and supplements are mostly alpha-tocopherol, which can, under some conditions, have a pro-oxidant effect. However, there is no evidence that taking supplements can block the antioxidant effect of vitamin E in food. Whether the pro-oxidant effect of alpha-tocopherol, which is also plentiful in food, has any biological importance is unclear.2