FAO/WHO expert consultation on human vitamin and mineral requirements 121 Chapter 9

Summary of the role of vitamin E in human metabolic processes large body of scientific evidence indicates that reactive free radicals are involved in many diseases, including heart disease and cancers (1). Cells contain many potentially oxidizable substrates such as polyunsaturated fatty acids (PUFAs), proteins, and DNA. Therefore, a complex antioxidant defence system normally protects cells from the injurious effects of endogenously produced free radicals as well as from species of exogenous origin such as cigarette smoke and pollutants. Should our exposure to free radicals exceed the protective capacity of the antioxidant defence system, a phenomenon often referred to as oxidative stress (2), then damage to biologic molecules may occur. There is considerable evidence that disease causes an increase in oxidative stress; therefore, consumption of foods rich in antioxidants, which are potentially able to quench or neutralise excess radicals, may play an important role in modifying the development of such diseases. Vitamin E is the major lipid-soluble antioxidant in the cell antioxidant defence system and is exclusively obtained from the diet. The term “vitamin E ” refers to a family of eight naturally occurring homologues that are synthesised by plants from homogentisic acid. All ar