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Vitamin A is a fat-soluble vitamin that is an essential nutrient. The term "vitamin A" encompasses a group of chemically related organic compounds that includes retinol , retinyl esters , and several provitamin (precursor) carotenoids , most notably β-carotene ( beta - carotene ).
Retinol, also called vitamin A 1, is a fat-soluble vitamin in the vitamin A family that is found in food and used as a dietary supplement. [3] Retinol or other forms of vitamin A are needed for vision, cellular development, maintenance of skin and mucous membranes , immune function and reproductive development. [ 3 ]
Retinyl acetate (retinol acetate, vitamin A acetate) is a natural [dubious – discuss] form of vitamin A which is the acetate ester of retinol. It has potential antineoplastic and chemopreventive activities.
β-Carotene is composed of two retinyl groups, and is broken down in the mucosa of the human small intestine by β-carotene 15,15'-monooxygenase to retinal,a form of vitamin A. β-Carotene can be stored in the liver and body fat and converted to retinal as needed, thus making it a form of vitamin A for humans and some other mammals.
Vitamin A supplementation of children under five who are at risk of VAD has been found to reduce all‐cause mortality by 12 to 24%. [30] Side effects of vitamin A supplements are rare. Vitamin A toxicity is a rare concern associated with high levels of vitamin A over prolonged periods of time.
It is genetic, like hair or eye color. Dense breast tissue not only makes mammograms more difficult to read, but it is also a risk factor for breast cancer. Women with dense breasts have a higher ...
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The basic structure of the hydrophobic retinoid molecule consists of a cyclic end group, a polyene side chain and a polar end group. The conjugated system formed by alternating C=C double bonds in the polyene side chain are responsible for the color of retinoids (typically yellow, orange, or red).