Vitamin E is the collective name for a set of eight related tocopherols and tocotrienols, which are fat-soluble vitamins with antioxidant properties.[1][2] Of these, α-tocopherol has been most studied as it has the highest bioavailability, with the body preferentially absorbing and using this form.[3]
It has been claimed that α-tocopherol is the most important lipid-soluble antioxidant, and that it protects cell membranes from oxidation by reacting with lipid radicals produced in the lipid peroxidationchain reaction.[1][4] This would remove the free radical intermediates and prevent the oxidation reaction from continuing. The oxidised α-tocopheroxyl radicals produced in this process may be recycled back to the active reduced form through reduction by other antioxidants, such as ascorbate, retinol or ubiquinol.[5]
The functions of the other forms of vitamin E are less well-studied, although γ-tocopherol is a nucleophile that may react with electrophilic mutagens,[3] and tocotrienols may have a specialized role in protecting neurons from damage.[6] However, the roles and importance of the various forms of vitamin E are presently unclear,[7][8] and it has even been suggested that the most important function of vitamin E is as a signaling molecule, and that it has no significant role in antioxidant metabolism.[9][10]
Most studies about Vitamin E have supplemented only alpha-tocopherol, but doing so leads to reduced serum gamma- and delta-tocopherol concentrations. For more info, read article tocopherol.
Food sources of Vitamin E
Particularly high levels of vitamin E can be found in the following foods:
^ Brigelius-Flohé R, Davies KJ (2007). "Is vitamin E an antioxidant, a regulator of signal transduction and gene expression, or a 'junk' food? Comments on the two accompanying papers: "Molecular mechanism of alpha-tocopherol action" by A. Azzi and "Vitamin E, antioxidant and nothing more" by M. Traber and J. Atkinson". Free Radic. Biol. Med.43 (1): 2–3. PMID 17561087.
^ Atkinson J, Epand RF, Epand RM (2007). "Tocopherols and tocotrienols in membranes: A critical review". Free Radic. Biol. Med.44 (5): 739-764. PMID 18160049.
