Vitamin E: current state of knowledge, role in the prevention of cardiovascular disease, bioavailability | La vitamine E: etat actuel des connaissances, role dans la prevention cardiovasculaire, biodisponibilite

Vitamin E is a generic term for a group of substances with a 6-OH-chroman nucleus. The most common one is the alpha-tocopherol and its natural form, the RRR-alpha-tocopherol stereoisomer. It has numerous functions. The antioxidant function is the most thoroughly studied and the best known. The role played by oxidized LDL and its oxidation in atherosclerosis and the fact that vitamin E is the major antioxidant in this lipoparticle have instigated in vitro, nutritional intervention and prospective cohort studies. They have led to establish that dietary vitamin E intake (only from food origin) is without effect on diminishing cardiovascular risk. Low doses of supplementation (50 IU/d) showed an effect in secondary prevention (morbidity) and no effect in primary prevention. Higher doses (330-400 IU/d) displayed a more pronounced effect in secondary prevention (morbidity) and could play a beneficial role on the mortality rate. However, a recent study showed a neutral effect of this supplementation level. The action on the cardiovascular risk is promising and plausible in terms of mechanisms of action. The bioavailability of vitamin E is rather high in the absence of lipid digestion and absorption and lipoprotein metabolism genetic disorders. Its safety at high and very high doses is explained by the presence of an hepatic recycling enzyme (the alpha-tocopherol transfer protein) which acts preferentially on the natural form RRR-alpha-tocopherol, and by an efficient mechanism for regenerating the reversibly oxidized form chromanoxyl. Future investigations will have to confirm the effects in secondary prevention and to initiate primary prevention trials as regards the cardiovascular diseases. They will have also to improve the knowledge and understanding of prevention regarding some forms of cancer, neurodegenerative diseases and age-related macular degeneration