Vitamin_e

The α-tocopherol form of vitamin E.

Main articles: tocopherol and tocotrienol

Vitamin E is the collective name for a set of eight related tocopherols and tocotrienols, which are fat-soluble vitamins with antioxidant properties.Herrera E, Barbas C (2001). "Vitamin E: action, metabolism and perspectives". J Physiol Biochem 57 (2): 43 – 56. PMID 11579997. Packer L, Weber SU, Rimbach G (2001). "Molecular aspects of alpha-tocotrienol antioxidant action and cell signalling". J. Nutr. 131 (2): 369S–73S. PMID 11160563.  Of these, α-tocopherol has been most studied as it has the highest bioavailability, with the body preferentially absorbing and using this form.Brigelius-Flohé R, Traber M (1999). "Vitamin E: function and metabolism". FASEB J 13 (10): 1145 – 55. PMID 10385606. 

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 peroxidation chain reaction.Traber MG, Atkinson J (2007). "Vitamin E, antioxidant and nothing more". Free Radic. Biol. Med. 43 (1): 4–15. PMID 17561088.  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.Wang X, Quinn P (1999). "Vitamin E and its function in membranes". Prog Lipid Res 38 (4): 309 – 36. PMID 10793887. 

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, and tocotrienols may have a specialized role in protecting neurons from damage.Sen C, Khanna S, Roy S (2006). "Tocotrienols: Vitamin E beyond tocopherols". Life Sci 78 (18): 2088 – 98. PMID 16458936.  However, the roles and importance of the various forms of vitamin E are presently unclear,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.  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.Azzi A (2007). "Molecular mechanism of alpha-tocopherol action". Free Radic. Biol. Med. 43 (1): 16–21. PMID 17561089. Zingg JM, Azzi A (2004). "Non-antioxidant activities of vitamin E". Curr. Med. Chem. 11 (9): 1113–33. PMID 15134510. 

Food sources of Vitamin E

Particularly high levels of vitamin E can be found in the following foods:

• Wheat germ
• Red Palm Oil
• Corn
• Nuts
• Seeds
• Olives
• Spinach and other green leafy vegetables
• Asparagus
• Vegetable oils -- corn, sunflower, soybean, cottonseed

References

External links

• Vitamin E Medline Plus, Medical Encyclopedia, U.S. National Library of Medicine
• Vitamin E Office of Dietary Supplements, National Institutes of Health

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