(redirected from Vitamin A deficiency)
Also found in: Dictionary, Thesaurus, Medical, Acronyms, Wikipedia.


see Vitamin A under vitaminvitamin,
group of organic substances that are required in the diet of humans and animals for normal growth, maintenance of life, and normal reproduction. Vitamins act as catalysts; very often either the vitamins themselves are coenzymes, or they form integral parts of coenzymes.
..... Click the link for more information.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(also called axerophthol or vitamin A), an isoprenoid whose chemical formula is C20H30O. Retinol is soluble in nonpolar organic solvents, insoluble in water, and has a melting point of 63°–64°C. In animals and man, it is converted from the carotene in food and stored mainly in the liver; it is particularly abundant in the liver of whales and fish and in fish oil.

The most important biological function of retinol is its participation in the form of retinal in the visual process. A retinol deficiency results in impairment of twilight vision (night blindness, or nyctalopia) and in injury to epithelial tissue, as in xe-rophthalmia. An excess of retinol causes a variety of metabolic disturbances, an accumulation of retinol in the hydrophobic fraction of cell membranes, and destruction of these membranes. Retinol is commercially synthesized from β-ionone. Retinol is sometimes called vitamin A1; its dehydro derivative C20H28O is called vitamin A2. Retinal1 and retinal2 are distinguished accordingly.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Prevalence of vitamin A deficiency was defined as low serum retinol concentrations (< 0.70 [micro]mol/l or < 20 [micro]g/dl) among children aged 0-4 years and among pregnant women (aged 15-49 years).
The prevalence of vitamin A deficiency in South African children aged 0-4 years was estimated at 33.8% using the SAVACG national data, which means that 1.8 million children were affected in 2000.
The population-attributable fractions (PAFs) for the selected health outcomes as well as the estimated number of cause-specific deaths and DALYs attributed to vitamin A deficiency among children aged 0-4 years are shown in Table II.
About 11% of all maternal mortality (222 deaths) was attributed to vitamin A deficiency. In addition to estimating the preventable deaths, attempts were also made to estimate attributable disease burden in children 0-4 years of age and pregnant women.
Vitamin A deficiency is a public health problem among preschool children in South Africa, with 33.8% of children aged 0-4 years being vitamin A-deficient.
Vitamin A deficiency accounted for 3 069 deaths in children aged 0-4 years (3.2% of all deaths in this age group).