Vitamin E | |
---|---|
Drug class | |
Class identifiers | |
Use | Vitamin E deficiency, antioxidant |
ATC code | A11HA03 |
Biological target | Reactive oxygen species |
Clinical data | |
Drugs.com | MedFacts Natural Products |
External links | |
MeSH | D014810 |
Legal status | |
In Wikidata |
Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols.[1][2] Vitamin E is classified as an essential nutrient for humans that is found naturally in some types of food and is also widely available as a nutritional supplement.[3] Vitamin E functions as a fat-soluble antioxidant which may help protect cell membranes from reactive oxygen species.[2][4] Various government organizations recommend that adults consume between 3 and 15 mg per day, whereas a worldwide review reported a median dietary intake of 6.2 mg per day.[5] Foods rich in vitamin E include seeds, nuts, seed oils, peanut butter, and vitamin E-fortified foods.[2][4] Symptomatic vitamin E deficiency is rare, is usually caused by an underlying problem with digesting dietary fat rather than from a diet low in vitamin E.[6] Deficiency can cause neurological disorders.[4]
Tocopherols and tocotrienols both occur in α (alpha), β (beta), γ (gamma), and δ (delta) forms, as determined by the number and position of methyl groups on the chromanol ring.[4][7] All eight of these vitamers feature a chromane double ring, with a hydroxyl group that can donate a hydrogen atom to reduce free radicals, and a hydrophobic side chain that allows for penetration into biological membranes. Both natural and synthetic tocopherols are subject to oxidation, so dietary supplements are esterified, creating tocopheryl acetate for stability purposes.[2][8]
Population studies have suggested that people who consumed foods with more vitamin E, or who chose on their own to consume a vitamin E dietary supplement, had lower incidence of cardiovascular diseases, cancer, dementia, and other diseases. However, placebo-controlled clinical trials using alpha-tocopherol as a supplement, with daily amounts as high as 2,000 mg per day, could not always replicate these findings.[2] In the United States vitamin E supplement use peaked around 2002, but had declined by more than half by 2006. Declining use was theorized to be due to publications of meta-analyses that showed either no benefits or actual negative consequences from high-dose vitamin E.[9][10][11][12][13][14]
Vitamin E was discovered in 1922, isolated in 1935, and first synthesized in 1938. Because the vitamin activity was first identified as essential for fertilized eggs to result in live births (in rats), it was given the name "tocopherol" from Greek words meaning birth and to bear or carry. Alpha-tocopherol, either naturally extracted from plant oils or, most commonly, as the synthetic tocopheryl acetate, is sold as a popular dietary supplement, either by itself or incorporated into a multivitamin product, and in oils or lotions for use on skin.
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