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Monday, February 14, 2011

vitamin E

Ellen Says: Vitamin E is a generic term for tocopherols which taken from the Greek words tokos,meaning offspring, and phero, meaning to bear, and tocotrienols.

Vitamin E is a family of alpha, beta, gamma, and delta) tocopherols and corresponding four tocotrienols.

Vitamin E is a fat-soluble antioxidant that stops the production of reactive oxygen species formed when fat undergoes oxidation.

Of these, α-tocopherol (also written as alpha-tocopherol) has been most studied as it has the highest bioavailability.

Gbex says: 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.

This would remove the free radical intermediates and prevent the oxidation reaction from continuing. The oxidized 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.

However, the importance of the antioxidant properties of this molecule at the concentrations present in the body are not clear and it is possible that the reason why vitamin E is required in the diet is unrelated to its ability to act as an antioxidant.

Other forms of vitamin E have their own unique properties. For example, tocopherol (also written as gamma-tocopherol) is a nucleophile that can react with electrophilic mutagens.

Alberto says: Compared with tocopherols, tocotrienols are sparsely studied. Less than 1% of PubMed papers on vitamin E relate to tocotrienols.

Current research direction is starting to give more prominence to the tocotrienols, the lesser known but more potent antioxidants in the vitamin E family.

Some studies have suggested that tocotrienols have specialized roles in protecting neurons from damage and cholesterol reduction by inhibiting the activity of HMG-CoA reductase; tocotrienol blocks processing of sterol regulatory element‐binding proteins.
Oral consumption of tocotrienols is also thought to protect against stroke-associated brain damage in vivo.

Until further research has been carried out on the other forms of vitamin E, conclusions relating to the other forms of vitamin E, based on trials studying only the efficacy of α-tocopherol, may be premature.

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