Vitamin E

Vitamin E
Drug class
The RRR alpha-tocopherol form of vitamin E
Class identifiers
UseVitamin E deficiency, antioxidant
ATC codeA11HA03
Biological targetReactive oxygen species
Clinical data
Drugs.comMedFacts Natural Products
External links
MeSHD014810
Legal status
In Wikidata

The term Vitamin E refers to a group of eight molecular-structure related compounds that include four tocopherols and four tocotrienols. The tocopherols function as fat-soluble antioxidants which may help protect cell membranes from reactive oxygen species. Vitamin E is classified as an essential nutrient for humans.[1] [2][3] Various government organizations recommend that adults consume between 3 and 15 mg per day, while a 2016 worldwide review reported a median dietary intake of 6.2 mg per day.[4] Sources rich in vitamin E include seeds, nuts, seed oils, peanut butter, vitamin E-fortified foods and dietary supplements.[3][1] 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.[5] Deficiency can cause neurological disorders.[1]

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.[1][6] 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.[3][7]

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.[3] 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[8][9][10] or actual negative consequences from high-dose vitamin E.[8][11][12]

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.

  1. ^ a b c d "Vitamin E Fact Sheet for Health Profesionals". Office of Dietary Supplements, U.S. National Institutes of Health. 12 July 2019. Retrieved 20 October 2024.
  2. ^ Traber MG, Bruno RS (2020). "Vitamin E". In Marriott BP, Birt DF, Stallings VA, Yates AA (eds.). Present knowledge in nutrition, eleventh edition. London, United Kingdom: Academic Press (Elsevier). pp. 115–36. ISBN 978-0-323-66162-1.
  3. ^ a b c d "Vitamin E". Micronutrient Information Center, Linus Pauling Institute, Oregon State University. October 2015. Retrieved 3 August 2019.
  4. ^ Cite error: The named reference Peter2016 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference DRItext was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Brigelius1999 was invoked but never defined (see the help page).
  7. ^ Braunstein MH (March 2006). Focus on vitamin E research. Nova Science Publishers. p. vii. ISBN 978-1-59454-971-7.
  8. ^ a b Kim HJ, Giovannucci E, Rosner B, Willett WC, Cho E (March 2014). "Longitudinal and secular trends in dietary supplement use: Nurses' Health Study and Health Professionals Follow-Up Study, 1986–2006". Journal of the Academy of Nutrition and Dietetics. 114 (3): 436–43. doi:10.1016/j.jand.2013.07.039. PMC 3944223. PMID 24119503.
  9. ^ Cite error: The named reference Abner2011 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Curtis2014 was invoked but never defined (see the help page).
  11. ^ Tilburt JC, Emanuel EJ, Miller FG (September 2008). "Does the evidence make a difference in consumer behavior? Sales of supplements before and after publication of negative research results". Journal of General Internal Medicine. 23 (9): 1495–8. doi:10.1007/s11606-008-0704-z. PMC 2518024. PMID 18618194.
  12. ^ Bjelakovic G, Nikolova D, Gluud C (2013). "Meta-regression analyses, meta-analyses, and trial sequential analyses of the effects of supplementation with beta-carotene, vitamin A, and vitamin E singly or in different combinations on all-cause mortality: do we have evidence for lack of harm?". PLOS ONE. 8 (9): e74558. Bibcode:2013PLoSO...874558B. doi:10.1371/journal.pone.0074558. PMC 3765487. PMID 24040282.