Definition Of Vitamin:
Vitamin A is a non-preserved nutrient organic ingredient consisting of Provitamin, retinal, retinal acid, and many protein-a-carbohydrates (especially beta carotene).
More About Vitamin:
Vitamin A has multiple functions: it is important for growth and development, for the preservation of the immune system and good vision. The retina needs vitamin A in the form of a retina, which is associated with the opsin protein for the formation of rhodopsin, the light absorbing molecule that is essential for low-light vision (scorpion vision) and color. Vitamin A also works in a very different function such as retinoic acid (an irreversible oxidized form of retinol), a significant growth hormone-like agent for epithelial and other cells.
In food of animal origin, the primary form of vitamin A is an ester, especially palmitic retinyl ester, which is converted to retinol (chemical alcohol) in the small intestine. The retinol form acts as a way of storing the vitamin and can be converted into and from the optically active form of the aldehyde, the retina.
All forms of vitamin A have a beta-ion ring to which an isoprenic chain, called a retinyl group, binds. Both structural features are essential for vitamin activity. The orange carrot pigment (β-carotene) can be represented as two linked retinyl groups, which are used in the body to contribute to vitamin A levels. Alpha-carotene and gamma-carotene also have a single retinyl group, gives them some vitamin. None of the other carotenes has a vitamin. Carotenoid beta-cryptoxanthin has an ion block and has vitaminic activity in humans.
Retinol, the form of vitamin A absorbed when eating food for animals, is a yellow matter soluble in fats. Since pure alcohol is unstable, vitamin is found in retinyl ester tissue. It is also commercially produced and administered as esters such as retinyl acetate or palmitine ester
Carotene alpha-carotene, β-carotene, γ-carotene. and xanthophyllite beta-cryptoxanthin (all containing beta-ions), but no other carotenoids, act as provitamin A in herbivorous and plague, possessing the β-carotene 15,15′-dioxigenase enzyme that cleaves beta carotene in the intestinal tract of the mucous membrane and It turns into retinol.
Since vitamin A is soluble in fats, release from excessive intake of food takes much longer than vitamin B and vitamin C. This allows the toxic levels of vitamin A to accumulate. These toxicities are produced only by those who have pre-formed vitamin A (retinoid) (such as in the liver). Carotenoid forms (such as beta-carotene in carrots) do not produce such symptoms, but excessive intake of beta-carotene can cause carotenoid, a harmless but aesthetically unpleasant orange-yellow color of the skin.
In general, acute toxicity occurs at a dosage of 25,000 IU / kg of body weight in general, and chronic toxicity occurs at 4,000 IU / kg of body weight daily for 6 to 15 months. However, liver toxicity can occur at as low levels as 15,000 IU (4500 micrograms) daily to 1.4 million IU daily, with a daily average toxic dose of 120,000 IU, especially in excessive alcohol consumption. In people with renal failure, 4000 IU can cause significant damage. Signs of toxicity may occur with long-term consumption of vitamin A at doses of 25,000 to 33,000 IU daily.
Excessive consumption of vitamin A can cause nausea, irritability, anorexia (decreased appetite), vomiting, blurred vision, headache, hair loss, muscle and abdominal pain, and nausea, drowsiness, and mental disorders. In chronic cases, hair loss, skin dryness, mucous membranes, fever, insomnia, fatigue, weight loss, bone fractures, anemia and diarrhea may be seen in addition to symptoms associated with less severe toxicity. Some of these symptoms are also common for the treatment of acne with isotretinoin. Chronic doses of vitamin A, as well as pharmaceutical retinoids, such as 13-cis retinoic acid, can produce pseudothyroid cerebral syndrome. This syndrome includes headache, blurred vision and confusion, associated with an increase in intracerebral pressure. Symptoms begin to be solved when harmful substance is introduced.
A chronic intake of 1500 RAE pre-formed vitamin A may be associated with osteoporosis and hip fractures, as it suppresses bone formation while stimulating bone degradation, although other reviews have called into question this effect, indicating that additional evidence is needed
A systematic review of 2012 found that beta-carotene and higher doses of supplemental vitamin A increase mortality in healthy people and people with various diseases. The findings of this review expand evidence that antioxidants may not have long-term benefits.
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