Vitamin E in the possible prevention of Alzheimer’s
(November 2005)

There have been multiple articles suggesting that various dietary components, estrogens, or physical activities can reduce the risk of Alzheimer’s, but no preventive has been adequately documented and most of the studies have substantial flaws. A new study in the American Journal of Clinical Nutrition suggesting the benefit of dietary vitamin E is quite well done. The investigators followed 1,041 men and women, average age 74 years; during a four-year followup, 162 developed Alzheimer’s. Vitamin E (which consists of several tocopherols) intake at enrollment was divided into the alpha (alpha tocopherol), gamma (gamma tocopherol), and beta (beta tocopherol) types. There was, for every 5 milligram increase in dietary total vitamin E intake or in intake of alpha tocopherol or gamma tocopherol, a reduction of 24 to 40 percent in risk of Alzheimer’s. Additionally, they examined the effects of dietary vitamin E on decline of mental (cognitive) function. Here again, an increase of 5 milligrams of dietary vitamin E, alpha tocopherol, or gamma tocopherol slowed the decline in cognitive function seen in the entire population studied. Although dietary vitamin E was beneficial, no reduction in risk was found with vitamin E supplements.

Commentary: This is a very interesting article. The lack of effect of vitamin E supplements is hard to explain. They contain large amounts of primarily alpha tocopherol and were ineffective, yet alpha tocopherol in the diet was effective in reducing risk of Alzheimer’s. The argument, in part, is that combinations of tocopherols (alpha, gamma, etc) are needed for reducing the likelihood of cognitive decline and Alzheimer’s and, therefore, giving supplements primarily of the alpha tocopherol component of vitamin E would not be expected to be effective. Whether that argument is valid is unclear.

It is not easy to get large amounts of vitamin E in the diet. For a long time, it was thought the alpha tocopherol form of vitamin E was the critical one, but, increasingly, the importance of the gamma tocopherol form has become apparent. When vitamin E supplements, containing mainly alpha tocopherol, are given, blood levels of gamma tocopherol fall. That may be undesirable. In the future, it is likely that vitamin E supplements will be combinations of alpha and gamma tocopherols.