vitamin A


vitamin A

noun

Definition of VITAMIN A

:  any of several fat-soluble vitamins (as retinol) found especially in animal products (as egg yolk, milk, or fish-liver oils) or a mixture of them whose lack in the animal body causes epithelial tissues to become keratinous (as in the eye with resulting visual defects)

First Known Use of VITAMIN A

circa 1920

vitamin A

noun    (Medical Dictionary)

Medical Definition of VITAMIN A

: any of several fat-soluble vitamins or a mixture of two or more of them whose lack in the animal body causes keratinization of epithelial tissues (as in the eye with resulting night blindness and xerophthalmia): as a : a pale yellow crystalline highly unsaturated alicyclic alcohol C20H29OH that is found in animal products (as egg yolk, milk, and butter) and especially in marine fish-liver oils (as of cod, halibut, and shark) and that is used in various forms in medicine and nutrition—called also retinol, vitamin A1 b : a yellow viscous liquid alicyclic alcohol C20H27OH that contains one more double bond in a molecule than vitamin A1 and is less active biologically in mammals and that occurs especially in the liver oil of freshwater fish—called also vitamin A2

vitamin A

noun    (Concise Encyclopedia)

Fat-soluble alcohol, most abundant in fatty fish and especially in fish-liver oils. It is not found in plants, but many vegetables and fruits contain beta-carotene (see carotene), which is readily converted in the body to vitamin A. It functions directly in vision, especially night vision. A derivative, retinaldehyde, is a component of the visual pigments, including rhodopsin, in the retina. Humans require vitamin A in very small amounts. Unlike carotenes, it is toxic in large amounts and is readily destroyed by exposure to heat, light, or air.

Variants of VITAMIN A

vitamin A also called retinol

Browse

Next Word in the Dictionary: vitamin B
Previous Word in the Dictionary: vitamin
All Words Near: vitamin A

Seen & Heard

What made you want to look up vitamin A? Please tell us where you read or heard it (including the quote, if possible).