Vitamin E - wikipedia Vitamin E Vitamin E Drug class The α - tocopherol form of vitamin E Class identifiers Use Vitamin E deficiency, antioxidant ATC code A11H Biological target Reactive oxygen species Clinical data Drugs.com MedFacts Natural Products External links MeSH D014810 In Wikidata Vitamin E refers to a group of compounds that include both tocopherols and tocotrienols. Of the many different forms of vitamin E, γ - tocopherol is the most common form found in the North American diet. γ - Tocopherol can be found in corn oil, soybean oil, margarine, and dressings. α - tocopherol, the most biologically active form of vitamin E, is the second-most common form of vitamin E in the diet. This variant can be found most abundantly in wheat germ oil, sunflower, and safflower oils. As a fat - soluble antioxidant, it interrupts the propagation of reactive oxygen species that spread through biological membranes or through a fat when its lipid content undergoes oxidation by reacting with more - reactive lipid radicals to form more stable products. U.S. and European Union recommendations are to consume, respectively, 15 mg / day or 11 mg / day ( female ) and 13 mg / day ( male ). Contents 1 Functions 1.1 Deficiency 2 Uses 2.1 Supplementation 2.2 Topical 3 Side effects 4 Diet 4.1 Recommendations 4.2 Food labeling 4.3 Sources 4.4 Supplements 4.5 Fortification 5 Chemistry 5.1 Tocopherols 5.2 Tocotrienols 6 Testing for levels 7 History 8 Notes 9 References 10 External links Functions Sample of α - tocopherol, one of the various forms of vitamin E, in an oil solution Vitamin E has many biological functions, including its role as a fat - soluble antioxidant. As an antioxidant, vitamin E acts as a peroxyl radical scavenger, disabling the production of damaging free radicals in tissues, by reacting with them to form a tocopheryl radical, which will then be reduced by a hydrogen donor ( such as vitamin C ) and thus return to its reduced state. As it is fat - soluble, it is incorporated into cell membranes, which protects them from oxidative damage. Vitamin E has also found use as a commercial antioxidant and biocompatible modifier of biomaterials and medical devices, for example in ultra high molecular weight polyethylene ( UHMWPE ) used in hip and knee implants by resisting oxidation and in hollow - fiber membrane cartridges used in extracorporeal hemodialysis therapy. As an enzymatic activity regulator, for instance, protein kinase C ( PKC ), which plays a role in smooth muscle growth, can be inhibited by α - tocopherol. α - Tocopherol has a stimulatory effect on the dephosphorylation enzyme, protein phosphatase 2A, which in turn, cleaves phosphate groups from PKC, leading to its deactivation, bringing the smooth muscle growth to a halt. Vitamin E also has an effect on gene expression. Macrophages rich in cholesterol are found in atherosclerotic tissue. Scavenger receptor CD36 is a class B scavenger receptor found to be up - regulated by oxidized low density lipoprotein ( LDL ) and binds it. Treatment with α - tocopherol was found to downregulate the expression of the CD36 scavenger receptor gene and the scavenger receptor class A ( SR - A ) and modulates expression of the connective tissue growth factor ( CTGF ). The CTGF gene, when expressed, is responsible for the repair of wounds and regeneration of the extracellular tissue lost or damaged during atherosclerosis. Vitamin E also plays a role in eye and neurological functions, and inhibition of platelet coagulation. Vitamin E also protects lipids and prevents the oxidation of polyunsaturated fatty acids. Although most vitamin E supplementation studies used α - tocopherol individually, this design of studying only one isoform of vitamin E may introduce errors in interpreting overall vitamin E effects ; for example, using only α - tocopherol in studies of inflammation can reduce serum γ - and δ - tocopherol concentrations. Moreover, a 2013 review involving single long - term supplementation with α - tocopherol showed that many clinical studies revealed an inverse relationship between supplementation and cardiovascular disease risk or mortality, but other studies showed no effect. Deficiency Main article : Vitamin E deficiency Vitamin E deficiency is rare in humans, occurring as a consequence of abnormalities in dietary fat absorption or metabolism rather than from a diet low in vitamin E. It can cause nerve problems due to poor conduction of electrical impulses along nerves due to changes in nerve membrane structure and function. Vitamin E deficiency can cause : peripheral neuropathy, myopathies, ataxia, retinopathy, impairment of immune responses and red blood cell destruction. Uses Supplementation Vitamin E supplementation has not been shown to have significant benefit for people who are healthy, and appears to be harmful. It does not improve blood sugar control in an unselected group of people with diabetes mellitus or decrease the risk of stroke. Daily supplementation of vitamin E does not decrease the risk of prostate cancer, and may increase it. Studies on its role in age - related macular degeneration are ongoing, though if it is of a combination of dietary antioxidants used to treat the condition it may increase the risk. Routine supplementation with vitamin E during pregnancy has been shown to offer no benefit to the mother or the child. Vitamin E has been reported to cause more side effects, such as abdominal pain in pregnant women, and also the increased risk of having early rupture of membranes at term. Supplementary Vitamin E, along with β - carotene and vitamin C, has shown no protective effect on reducing the risk of cataract, cataract extraction, progression of cataract, and slowing the loss of visual acuity. A meta - analysis showed no association between vitamin E supplementation and cardiovascular mortality. A 2015 systematic review found that it may improve endothelial function as determined by measurements of forearm blood flow, but when combined with vitamin C supplementation, it did not. Topical Although there is widespread use of vitamin E as a topical medication, with claims for improved wound healing and reduced scar tissue, reviews have repeatedly concluded that there is insufficient evidence to support these claims. Side effects The US Food and Nutrition Board has set a Tolerable upper intake level ( UL ) at 1,000 mg ( 1,500 IU ) per day. The European Food Safety Authority reviewed the same safety question and set a UL at 300 mg / day. Vitamin E can act as an anticoagulant, increasing the risk of bleeding, specifically acting synergistically with the blood - thinner, warfarin, which acts as a vitamin K antagonist. From a 1982 review, vitamin E was reported as not having an anti-coagulation effect in humans who were vitamin K status sufficient. Although functioning as an antioxidant when consumed in amounts available from foods, in high doses possible with dietary supplement products, vitamin E can have prooxidant properties, possibly causing oxidation which may damage cells and increase the risk of cancer. Supplementation with vitamin E is not indicated during treatment with chemotherapy or radiotherapy. Long - term use of high doses may cause nausea, diarrhea and blurred vision. The US National Institutes of Health, Office of Dietary Supplements, summarizes the research on health risks from excessive vitamin E. Diet Recommendations The U.S. Institute of Medicine ( IOM ) updated Estimated Average Requirements ( EARs ) and Recommended Dietary Allowances ( RDAs ) for vitamin E in 2000. The current EAR for vitamin E for women and men ages 14 and up is 12 mg / day. The RDA is 15 mg / day. RDAs are higher than EARs so as to identify amounts that will cover people with higher than average requirements. RDA for pregnancy is 15 mg / day. RDA for lactation is 19 mg / day. For infants up to 12 months the Adequate Intake ( AI ) is 4 -- 5 mg / day. For children ages 1 -- 13 years the RDA increases with age from 6 to 11 mg / day. As for safety, the IOM sets Tolerable upper intake levels ( ULs ) for vitamins and minerals when evidence is sufficient. Hemorrhagic effects in rats were selected as the critical endpoint to calculate the UL via starting with the lowest - observed - adverse - effect - level ( LOAEL ) and processing that through an uncertainty factor calculation. The end result was the UL set at 1000 mg / day. Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes ( DRIs ). The European Food Safety Authority ( EFSA ) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake ( PRI ) instead of RDA, and Average Requirement instead of EAR. AI and UL defined the same as in United States. For women and men ages 10 and older the PRIs are set at 11 and 13 mg / day, respectively. PRI for pregnancy is 11 mg / day, for lactation 11 mg / day. For children ages 1 -- 9 years the PRIs increase with age from 6 to 9 mg / day. These PRIs are lower than the U.S. RDAs. The European Food Safety Authority reviewed the same safety question and set a UL at 300 mg / day. The EU used an effect on blood clotting as a critical effect, identified that no adverse effects were observed in a human trial as 540 mg / day, used an uncertainty factor of 2 to get to a suggest UL of 270 mg / day, then rounded up to 300 mg / day. The Japan National Institute of Health and Nutrition set lower AIs than the US RDAs or EU PRIs, and intermediate ULs : 6.5 mg / day ( females ) and 7.0 mg / day ( males ) for adult AIs, and 650 - 700 mg / day ( females ) and 750 - 900 mg / day ( males ) for adult ULs, amount depending on age. India recommends an intake of 8 - 10 mg / day and does not set a UL. A worldwide summary of more than one hundred studies reported a median dietary intake of 6.2 mg / d for alpha - tocopherol. Government survey results in the US reported average consumption for adult females at 8.4 mg / d and adult males 10.4 mg / d. Average consumption is below recommendations. Food labeling For U.S. food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of Daily Value ( % DV ). For vitamin E labeling purposes 100 % of the Daily Value was 30 IU, but as of May 27, 2016 it was revised to 15 mg to bring it into agreement with the RDA. A table of the old and new adult Daily Values is provided at Reference Daily Intake. The original deadline to be in compliance was July 28, 2018, but on September 29, 2017 the FDA released a proposed rule that extended the deadline to January 1, 2020 for large companies and January 1, 2021 for small companies. European Union regulations require that labels declare energy, protein, fat, saturated fat, carbohydrates, sugars, and salt. Voluntary nutrients may be shown if present in significant amounts. Instead of Daily Values, amounts are shown as percent of Reference Intakes ( RIs ). For vitamin E, 100 % RI was set at 12 mg in 2011. Sources mg / ( 100 g ) Some foods with vitamin E content low high 150 Wheat germ oil 95 Almond oil 44 Canola / rapeseed oil 41 Sunflower oil 34 Safflower oil 26 Almonds 19 Wheat germ 15 Hazelnuts 14 Olive oil 8.33 Peanut 1.5 3.4 High - value green, leafy vegetables : spinach, turnip, beet greens, collard greens, and dandelion greens 2.32 Butter Avocados 1.8 Cocoa butter 1.4 Sesame oil 1.1 1.5 Asparagus 1.5 Kiwifruit ( green ) 0.90 Cashew nuts 0.78 1.5 Broccoli 0.8 Pumpkin 0.26 0.94 Sweet potato 0.9 Mangoes 0.7 Walnuts 0.54 0.56 Tomatoes 0.13 0.22 Low - value green, leafy vegetables : lettuce Supplements Vitamin E is fat soluble, so dietary supplement products are usually in the form of the vitamin dissolved in vegetable oil in a softgel capsule. For alpha - tocopherol, amounts range from 100 to 1000 IU per serving. Smaller amounts are incorporated into multi-vitamin / mineral tablets. Gamma - tocopherol and tocotrienol supplements are available from a few dietary supplement companies. Fortification The World Health Organization does not have any recommendations for food fortification with vitamin E. The Food Fortification Initiative does not list any countries that have mandatory or voluntary programs for vitamin E. There are breakfast cereals fortified with minerals and vitamins, including vitamin E. Chemistry The nutritional content of vitamin E is defined by α - tocopherol activity. The molecules that contribute α - tocopherol activity are four tocopherols and four tocotrienols, identified by the prefixes alpha - ( α - ), beta - ( β - ), gamma - ( γ - ), and delta - ( δ - ). Natural tocopherols occur in the RRR - configuration only. The synthetic form contains eight different stereoisomers and is called ' all - rac ' - α - tocopherol. Form Structure alpha - Tocopherol beta - Tocopherol gamma - Tocopherol delta - Tocopherol Tocopherols General chemical structure of tocotrienols. alpha - Tocopherol is a lipid - soluble antioxidant functioning within the glutathione peroxidase pathway, and protecting cell membranes from oxidation by reacting with lipid radicals produced in the lipid peroxidation chain reaction. This removes the free radical intermediates and prevents the oxidation reaction from continuing. The oxidized 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. Other forms of vitamin E have their own unique properties ; for example, γ - tocopherol is a nucleophile that can react with electrophilic mutagens. Tocotrienols The four tocotrienols ( alpha, beta, gamma, delta ) are similar in structure to the four tocopherols, with the main difference being that the former have hydrophobic side chains with three carbon - carbon double bonds, whereas the tocopherols have saturated side chains. For alpha ( α ) - tocotrienol each of the three `` R '' sites has a methyl group ( CH ) attached. For beta ( β ) - tocotrienol : R1 = Methyl, R2 = H, R3 = Methyl. For gamma ( γ ) - tocotrienol : R1 = H, R2 = Methyl, R3 = Methyl. For delta ( δ ) - tocotrienol : R1 = H, R2 = H, R3 = Methyl. Palm oil is a source. Preliminary clinical trials on dietary supplement tocotrienols indicate potential for anti-disease activity. Testing for levels Cystic fibrosis and other fat malabsorption conditions can result in low serum vitamin E and dietary supplements will raise serum vitamin E. A normal range for serum alpha - tocopherol has been described as 5 -- 20 mg / L and low as < 2.0 mg / L. A worldwide summary of more than one hundred studies reported a median of 9.5 mg / L for alpha - tocopherol and a desired range of more than 12.9 mg / L ( 30 μmol / L ). History Vitamin E was discovered in 1922 by Herbert McLean Evans and Katharine Scott Bishop and first isolated in a pure form by Evans and Gladys Anderson Emerson in 1935 at the University of California, Berkeley. Because the vitamin activity was first identified as a dietary fertility factor ( in rats ) it was given the name `` tocopherol '' from the Greek words `` τόκος '' ( tókos, birth ), and `` φέρειν '', ( phérein, to bear or carry ) meaning in sum `` to carry a pregnancy, '' with the ending `` - ol '' signifying its status as a chemical alcohol. George M. Calhoun, Professor of Greek as the University of California, was credited with helping with the naming process. Erhard Fernholz elucidated its structure in 1938 and shortly afterwards the same year, Paul Karrer and his team first synthesized it. Nearly 50 years after the discovery of vitamin E an editorial in the Journal of the American Medical Association titled `` Vitamin in search of a disease '' read in part ``... research revealed many of the vitamin 's secrets, but no certain therapeutic use and no definite deficiency diease in man. '' The animal discovery experiments had been a requirement for successful pregnancy, but no benefits were observed for women prone to miscarriage. Evidence for vascular health was characterized as unconvincing. The editorial closed with mention of some preliminary human evidence for protection against hemolytic anemia in young children. A role for vitamin E in coronary heart disease had first been proposed in 1946. More cardiovascular work from the same research group followed, including a proposal that megadoses of vitamin E could slow down and even reverse the development of atherosclerosis. However, a 2004 meta - analysis showed no association between vitamin E supplementation and cardiovascular events ( nonfatal stroke or myocardial infarction ) or cardiovascular mortality. There is a long history of belief that topical application of vitamin E containing oil benefits burn and wound healing. This belief persists even though scientific reviews repeatedly refuted this claim. The role of vitamin E in infant nutrition has a long research history. From 1949 onward there were trials with premature infants suggesting that oral alpha - tocopherol was protective against edema, intracranial hemorrhage, hemolytic anemia and retrolental fibroplasia. A 2003 Cochrane review concluded that vitamin E supplementation in preterm infants reduced the risk of intercranial hemorrhage and retinopathy, but noted an increased risk of sepsis. Notes Jump up ^ `` USDA Nutrient Data Laboratory ''. In notes 2 -- 11, USDA NDL Release 24 numbers are given as mg / ( 100 g ). Low and high values vary some by raw versus cooked and by variety. Jump up ^ Spinach ( 2.0 raw, 2.1 cooked ), turnip ( 2.9 raw, 1.9 cooked ), beet ( 1.5 raw, 1.8 cooked ), collard ( 2.3 raw, 0.88 cooked ), and dandelion greens ( 3.4 raw, 2.4 cooked ) Jump up ^ 1.1 raw, 1.5 cooked Jump up ^ 0.78 raw, 1.5 cooked Jump up ^ 1. raw, 0.8 cooked Jump up ^ 0.26 raw, 0.94 boiled Jump up ^ 0.54 raw, 0.56 cooked Jump up ^ Lettuce ( 0.18 iceberg, 0.22 green leaf, 0.13 romaine, 0.15 red leaf, 0.18 butterhead ) References ^ Jump up to : `` Vitamin E -- Health Professional Fact Sheet ''. Office of Dietary Supplements, US National Institutes of Health. 9 May 2016. Retrieved 5 February 2015. Jump up ^ Brigelius - Flohé R, Traber MG ( 1999 ). `` Vitamin E : function and metabolism '' ( PDF ). FASEB J. 13 ( 10 ) : 1145 -- 1155. PMID 10385606. ^ Jump up to : `` Vitamin E ''. Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. May 2015. 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CS1 maint : Multiple names : authors list ( link ) External links Vitamins ( A11 ) Fat soluble α - Carotene β - Carotene Retinol Tretinoin Ergosterol Ergocalciferol 7 - Dehydrocholesterol Previtamin D Cholecalciferol 25 - hydroxycholecalciferol Calcitriol ( 1, 25 - dihydroxycholecalciferol ) Calcitroic acid Dihydroergocalciferol D analogues Alfacalcidol Dihydrotachysterol Calcipotriol Tacalcitol Paricalcitol Tocopherol Alpha Beta Gamma Delta Tocotrienol Alpha Beta Gamma Delta Tocofersolan Naphthoquinone Phylloquinone ( K ) Menaquinones ( K ) Menadione ( K ) ‡ Menadiol ( K ) Water soluble Thiamine B analogues Acefurtiamine Allithiamine Fursultiamine Octotiamine Prosultiamine Sulbutiamine Riboflavin Niacin Nicotinamide Pantothenic acid Dexpanthenol Pantethine Pyridoxine, Pyridoxal phosphate Pyridoxamine Pyritinol Biotin Folic acid Dihydrofolic acid Folinic acid Levomefolic acid Adenosylcobalamin Cyanocobalamin Hydroxocobalamin Methylcobalamin Choline Ascorbic acid Dehydroascorbic acid Combinations Multivitamins WHO - EM Withdrawn from market Clinical trials : Phase III Never to phase III Antioxidants Food antioxidants 6 - Hydroxymelatonin Acetyl - L - carnitine ( ALCAR ) Alpha - lipoic acid ( ALA ) Ascorbic acid ( vitamin C ) Carotenoids ( vitamin A ) Curcumin Edaravone Polyphenols Glutathione Hydroxytyrosol L - carnitine Ladostigil Melatonin Mofegiline N - Acetylcysteine ( NAC ) N - Acetylserotonin ( NAS ) Oleocanthal Oleuropein Rasagiline Resveratrol Selegiline Selenium Tocopherols ( vitamin E ) Tocotrienols ( vitamin E ) Tyrosol Ubiquinone ( coenzyme Q ) Uric acid Fuel antioxidants Butylated hydroxytoluene 2, 6 - Di - tert - butylphenol 1, 2 - Diaminopropane 2, 4 - Dimethyl - 6 - tert - butylphenol Ethylenediamine Measurements Folin method ORAC TEAC FRAP NDL : 00560695 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Vitamin_E&oldid=828287429 '' Categories : Food antioxidants Vitamin E Vitamins Bicyclic compounds Hidden categories : CS1 maint : Multiple names : authors list CS1 maint : Uses authors parameter Webarchive template wayback links CS1 maint : Uses editors parameter Template : drugs.com link with non-standard subpage All articles with unsourced statements Articles with unsourced statements from February 2018 Use dmy dates from June 2012 Talk Contents About Wikipedia Afrikaans Asturianu Български Català Čeština Dansk Deutsch ދިވެހިބަސް Eesti Español Esperanto Euskara فارسی Français Galego 한국어 Հայերեն हिन्दी Hrvatski Bahasa Indonesia עברית Basa Jawa ქართული Қазақша Кыргызча Latviešu Lietuvių Македонски മലയാളം मराठी Nederlands नेपाली 日本 語 Norsk Occitan ਪੰਜਾਬੀ Polski Русский Scots සිංහල Simple English Slovenčina Slovenščina Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska தமிழ் ไทย Türkçe Тыва дыл Українська ئۇيغۇرچە / Uyghurche Tiếng Việt 中文 47 more Edit links This page was last edited on 1 March 2018, at 17 : 52. 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Question: the most active form of vitamin e is
Answer: α-tocopherol