[Is vitamin-E supplementation beneficial or harmful?]

Even though the beneficial effects of vitamin E have been experimentally observed, some clinical trials failed to verify a consistent benefit. One reason for this situation has been the difficulty to make comparisons among different studies. There are differences due to subjects, chemical forms of vitamin E, stages of the disease and others. The intake of high doses of vitamin E as a supplement has increased in many countries. Novel studies, have informed that vitamin E not only has antioxidant properties but can acts through precise molecular actions interacting with proteins and enzymes and modulating cellular signaling, transcriptional regulation and apoptosis induction. However, some recent clinical and meta analysis studies have found that daily supplementation with vitamin E 400 IU or higher is associated to increased mortality. In conclusion, a complete understanding of vitamin E actions at the cell does not exist yet and the controversy about its clinical effects is still present. This paper offers current knowledge on the characteristics, metabolism, properties, beneficial effect as well as the potential toxicity of vitamin E.