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Vitamin E

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**Chemistry and Biosynthesis**:
Vitamin E is a group of eight fat-soluble compounds consisting of four tocopherols and four tocotrienols.
– Tocopherols and tocotrienols have different chemical structures based on the position of methyl groups and the saturation of their side chains.
– Biosynthesis of vitamin E starts with homogentisic acid and involves the Shikimate and MEP pathways.
– Tocopherols have saturated side chains, while tocotrienols have polyunsaturated side chains.
– Plants synthesize tocochromanols for antioxidant activity, with gamma-tocopherol being created first, leading to alpha- or delta-tocopherol.

**Function and Benefits**:
Vitamin E acts as a fat-soluble antioxidant by donating hydrogen atoms to radicals.
– It plays various roles in gene expression, enzyme activity regulation, and deactivating protein kinase C to inhibit smooth muscle growth.
– Tocochromanols protect against UV radiation damage and promote seed longevity and successful germination.
– Benefits of vitamin E include powerful antioxidant properties, immune function support, skin health, and potential reduction in the risk of chronic diseases.
– Essential under stressed growing conditions and for overall health and well-being.

**Sources and Intake**:
– Gamma-tocopherol is common in the North American diet, while palm oil is a source of tocotrienols.
– Various plant oils, nuts, fish, eggs, and fortified foods are rich sources of vitamin E.
– Recommended daily intake varies from 10-19 mg for different age groups and conditions.
Vitamin E amount on food labels is shown as a percentage of daily value, with the US using international units for measurement until May 2016.
– EU regulations require certain nutrients to be shown as a percentage of reference intakes.

**Supplements and Fortification**:
Vitamin E supplements are commonly in the form of tocopheryl acetate, ranging from 100 to 1000 IU per serving.
– Gamma-tocopherol and tocotrienol supplements are available, with tocotrienols extracted from palm oil.
– WHO does not recommend food fortification with vitamin E, but infant formulas and certain foods may contain added alpha-tocopherol.
– Multi-vitamin/mineral tablets may contain smaller amounts of alpha-tocopherol.
– Food fortification initiatives do not list countries with fortification programs.

**Metabolism and Industrial Synthesis**:
– Tocopherols and tocotrienols are absorbed in the intestine, metabolized, and excreted via urine.
– Alpha-tocopherol is preferentially taken up by alpha-tocopherol transfer protein for metabolism.
– Synthetic vitamin E is all-rac-alpha-tocopherol, synthesized from toluene and 2,3,5-trimethyl-hydroquinone.
– It consists of 8 stereoisomers in equal quantities and has 73.5% potency of natural vitamin E.
– Synthetic vitamin E is converted to ester form for stability in dietary supplements and fortified foods.

Vitamin E (Wikipedia)

Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vitamin E, can cause nerve problems. Vitamin E is a fat-soluble antioxidant which may help protect cell membranes from reactive oxygen species. Worldwide, government organizations recommend adults consume in the range of 3 to 15 mg per day. As of 2016, consumption was below recommendations according to a worldwide summary of more than one hundred studies that reported a median dietary intake of 6.2 mg per day for alpha-tocopherol.

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
Legal status
In Wikidata

Population studies 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. In the United States vitamin E supplement use peaked around 2002, but has declined by more than half by 2006. The authors theorized that declining use may have been due to publications of large placebo-controlled studies that showed either no benefits or actual negative consequences from high-dose vitamin E.

Both natural and synthetic tocopherols are subject to oxidation, so dietary supplements are esterified, creating tocopheryl acetate for stability purposes. 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. 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.

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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