22 Facts About Vitamin A

Vitamin A has multiple functions: it is essential for embryo development and growth, for maintenance of the immune system, and for vision, where it combines with the protein opsin to form rhodopsin – the light-absorbing molecule necessary for both low-light and color vision.

Vitamin A deficiency is common in developing countries, especially in Sub-Saharan Africa and Southeast Asia.

Vitamin A deficiency is estimated to affect approximately one-third of children under the age of five around the world, resulting in hundreds of thousands of cases of blindness and deaths from childhood diseases because of immune system failure.

Vitamin A toxicity referred to as hypervitaminosis A, occurs when there is too much vitamin A accumulating in the body.

Vitamin A is a fat-soluble vitamin, a category that includes vitamins D, E and K The vitamin encompasses several chemically related naturally occurring compounds or metabolites, i e, vitamers, that all contain a ß-ionone ring.

Related searches

Retinol – the transport and storage form of vitamin A – is interconvertible with retinal, catalyzed to retinal by retinol dehydrogenases and back to retinol by retinaldehyde reductases.

Vitamin A status involves eye health via two separate functions.

Vitamin A deficiency caused night blindness is a reversible difficulty for the eyes to adjust to dim light.

Xerophthalmia, caused by a severe vitamin A deficiency, is described by pathologic dryness of the conjunctival epithelium and cornea.

The prevalence of pre-school age children who are blind due to vitamin A deficiency is lower than expected from incidence of new cases only because childhood vitamin A deficiency significantly increases all-cause mortality.

Vitamin A deficiency has been linked to compromised resistance to infectious diseases.

Deficiencies in vitamin A have been linked to an increased susceptibility to skin infection and inflammation.

Vitamin A appears to modulate the innate immune response and maintains homeostasis of epithelial tissues and mucosa through its metabolite, retinoic acid .

Vitamin A toxicity hypervitaminosis A occurs when too much vitamin A accumulates in the body.

Vitamin A deficiency is common in developing countries, especially in Sub-Saharan Africa and Southeast Asia.

Vitamin A deficiency is "the leading cause of preventable childhood blindness", according to UNICEF.

The amount of vitamin A leaving the liver, bound to retinol binding protein, is under tight control as long as there are sufficient liver reserves.

The enzyme is lacking in felids, meaning that vitamin A requirements are met from the retinyl ester content of prey animals.

Malaria and vitamin A deficiency are both common among young children in sub-Saharan Africa.

For malaria, clinical trial results are mixed, either showing that vitamin A treatment did not reduce the incidence of probable malarial fever, or else did not affect incidence, but did reduce slide-confirmed parasite density and reduced the number of fever episodes.

Researchers proposed several mechanisms by which malaria could contribute to vitamin A deficiency, including a fever-induced reduction in synthesis of retinal-binding protein responsible for transporting retinol from liver to plasma and tissues, but reported finding no evidence for a transient depression or restoration of plasma RBP or retinol after a malarial infection was eliminated.

Vitamin A suggested that this substance, by a photochemical process, conveyed the impression of light to the brain.