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Viridian Vitamins | Vitamin E Cream | Vitamins And Minerals Online | healthstore.uk.com | natural vitamins,multiple vitamins,health food... sweetmedicineessentials.c... | Vitamins And Vision Loss Vitamin E Vitamin C Beta Carotene Zinc Copper healthbulletin.org |
 Main articles: tocopherol and tocotrienol Vitamin E is a generic term for tocopherols and tocotrienols.[1] Vitamin E is a family of α-, β-, γ-, and δ-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.[2][3][4] Of these, α-tocopherol (also written as alpha-tocopherol) has been most studied as it has the highest bioavailability.[5]
[edit] α-tocopherolIt 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.[3][6] 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.[7] 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.[8]. Other forms of vitamin E have their own unique properties. For example, γ-tocopherol (also written as gamma-tocopherol) is a nucleophile that can react with electrophilic mutagens.[5] However, the roles and importance of all of the various forms of vitamin E are presently unclear,[9][10] 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.[11][12] So far, most studies about vitamin E have supplemented using only the synthetic alpha-tocopherol, but doing so leads to reduced serum gamma- and delta-tocopherol concentrations. Moreover, a 2007 clinical study involving synthetic alpha-tocopherol concluded that supplementation did not reduce the risk of major cardiovascular events in middle aged and older men.[13] For more info, read article tocopherol. [edit] Tocotrienols
Compared with tocopherols, tocotrienols are poorly studied.[14][15][16] Less than 1% of PubMed papers on vitamin E relate to tocotrienols.[17] Current research direction are starting to give more prominence to the tocotrienols, the lesser known but more potent antioxidants in the vitamin E family. Tocotrienols have specialized roles in protecting neurons from damage[18], cancer prevention[19] and cholesterol reduction[20] by inhibiting the activity of HMG-CoA reductase[16-1];δ-tocotrienol blocks processing of sterol regulatory element‐binding proteins (SREBPs)[16-1]. Oral consumption of tocotrienols is also proven to protect against stroke-associated brain damage in vivo. Disappointments with outcomes-based clinical studies testing the efficacy of α-tocopherol need to be handled with caution and prudence recognizing the untapped opportunities offered by the other forms of natural vitamin E.[21] Toxicity studies of a specific form of tocopherol in excess should not be used to conclude that high-dosage “vitamin E” supplementation may increase all-cause mortality. Such conclusion incorrectly implies that tocotrienols are toxic as well under conditions where tocotrienols were not even considered.[22] For more info, read article tocotrienol. [edit] Food sources of Vitamin EParticularly high levels of vitamin E can be found in the following foods:[23]
[edit] Health effects of dietary Vitamin E[edit] Vitamin E to prevent prostate cancer study discontinuedThere have been some theories that Vitamin E, especially when coupled with selenium, may reduce the risk of prostate cancer[24] by 30 percent.[25] However, the Selenium and Vitamin E Cancer Prevention Trial, ("SELECT"), run from 2004 to 2008, found that vitamin E, whether taken alone or in combination with selenium, did not prevent prostate cancer.[26] The SELECT study was discontinued after independent reviewers determined that there was no benefit to the 35,000 men who were the subject of the study. [24] [edit] Congenital heart defectsA case control study done in the Netherlands using food frequency questionnaires found that high maternal Vitamin E by diet and supplements is associated with an increased risk of CHD (congenital heart defects) offspring, especially when the supplements are taken in the periconception period.[27] (Note: case control studies are rated as low quality, grade 3 or 4, on a standard scale of medical evidence.[28]) The National Health Service in the United Kingdom concludes that pregnant women should: "consider avoiding taking supplemental Vitamin E tablets."[29] [edit] Vitamin E and strokesA Finnish study found that Vitamin E supplementation increased the risk of hemorrhagic stroke (The Alpha-Tocopherol Beta-Carotene Cancer Prevention Study Group. The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. N Engl J Med 1994;330:1029–35.) Vitamin E supplementation was shown to increase the risk of heart failure in a 2005 study published in the Journal of the American Medical Association by Lonn, et al., which studied 7,000 people (JAMA. 2005 Mar 16;293(11):1338-47. Effects of long-term vitamin E supplementation on cardiovascular events and cancer: a randomized controlled trial.) [edit] References
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