The role of vitamin E in the diet.
2008
Shrapnel, B. S.
The last decade has seen many developments in our understanding of vitamin E, its transport and metabolism, and its potential role in the prevention of chronic disease. Of the eight fat-soluble substances comprising vitamin E, alpha-tocopherol has emerged as central to vitamin E activity in the body, its concentration in the plasma being governed by alpha-tocopherol transfer protein and maintained in a narrow range. Although new insights into the role of habitual fat intake in determining human requirements for vitamin E have been gained, uncertainties remain and estimates of requirements differ considerably between authorities. Investigation of the potential of this potent chain-breaking antioxidant to prevent or delay conditions thought to be associated with oxidative stress, including cardiovascular disease, cancer, Alzheimer's disease and Parkinson's disease, has challenged nutritionists to reconsider optimal intakes of vitamin E. High-dose supplementation has proved ineffective in reducing risk and may even be associated with increased risk; yet, new evidence suggests that a lifetime diet rich in alpha-tocopherol may provide protection against heart disease and cancer. Intakes of alpha-tocopherol are low in some western populations, which may in part be the result of advice to consume low-fat diets, intended to help address rising rates of obesity. An increased focus on fat quality, consistent with advice stemming from the cardiovascular literature, will help ensure adequate intakes of vitamin E in the context of diets moderate in total fat.
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