The term vitamin E represents a group of fat-soluble vitamins with antioxidant activity. This group includes eight different forms (alpha, beta, gamma, and delta tocopherols and alpha, beta, gamma, and delta tocotrienols) with different degrees of biologic activity. Alpha-tocopherol is the only form that meets human needs.
Vitamin E's biologic effect is due to its antioxidant properties and its protective role on membrane cells lipids and phospholipids. A number of studies have proven its beneficial effect on the nervous system, on muscles and the cardiovascular system, on neuro-vegetative disorders (Pallast, 1999), as well as on the immune response (Pae, 2012; De la Fuente, 2008; Meydani, 2005). Vitamin E enhances vitamin A action while its assimilation is stimulated by vitamin C and selenium. By contrast, iron intake decreases its bioavailability; if PUFAs are present, vitamin E is required over a certain minimum level.
The effect of vitamin E supplementation on neuro-vegetative disorders, such as Alzheimer's, is being investigated. Since the 1990s, clinical trials have confirmed an immune response improvement in the elderly (Meydani, 1990; Meydani, 1997).
Even though positive effects are clearly recognized by the scientific community, over the last few years some studies have proven that a high dosage of vitamin E supplements may increase mortality due to potential toxicity (Miller, 2005; Bjelakovic, 2007; Galli, 2010). High amounts of this vitamin, together with low levels of vitamin K or of anticoagulants, can decrease coagulation time and can lead to muscular weakening and fatigue. Many epidemiological studies link high vitamin E concentrations to a mortality increase (Bjelakovic, 2014). After a review of over 300 articles, the Institute of Medicine (IOM, United States National Academies) confirmed that vitamin E is very well tolerated by humans and that an amount of approx. 1000 mg/ die is safe. The Scientific Committee on Food (SCF, European Commission) identified a No Observed Adverse Effect Level (NOAEL) around 300 mg a-TE/die (EFSA, 2015).