Vitamin A is the name of a group of fat-soluble retinoids, including retinol, retinal, and retinyl esters [ 1-3 ]. Vitamin A is involved in immune function, vision, reproduction, and cellular communication [ 1 , 4 , 5 ]. Vitamin A is critical for vision as an essential component of rhodopsin, a protein that absorbs light in the retinal receptors, and because it supports the normal differentiation and functioning of the conjunctival membranes and cornea [ 2-4 ]. Vitamin A also supports cell growth and differentiation, playing a critical role in the normal formation and maintenance of the heart, lungs, kidneys, and other organs [ 2 ].

The various forms of vitamin A are solubilized into micelles in the intestinal lumen and absorbed by duodenal mucosal cells [ 5 ]. Both retinyl esters and provitamin A carotenoids are converted to retinol, which is oxidized to retinal and then to retinoic acid [ 2 ]. Most of the body's vitamin A is stored in the liver in the form of retinyl esters.

A plasma retinol concentration lower than 0.70 micromoles/L (or 20 micrograms [mcg]/dL) reflects vitamin A inadequacy in a population, and concentrations of 0.70–1.05 micromoles/L could be marginal in some people [ 5 ]. In some studies, high plasma or serum concentrations of some provitamin A carotenoids have been associated with a lower risk of various health outcomes, but these studies have not definitively demonstrated that this relationship is causal.

This document is a supplement to the Guidance Document for developing and assessing Adverse Outcome Pathways (AOPs). It provides focused and practical instructions for both AOP developers and reviewers and is intended to assist in identifying, organising and evaluating critical information on...

(Definition of “supplement” from the Cambridge Advanced Learner’s Dictionary & Thesaurus © Cambridge University Press)

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Vitamin A is the name of a group of fat-soluble retinoids, including retinol, retinal, and retinyl esters [ 1-3 ]. Vitamin A is involved in immune function, vision, reproduction, and cellular communication [ 1 , 4 , 5 ]. Vitamin A is critical for vision as an essential component of rhodopsin, a protein that absorbs light in the retinal receptors, and because it supports the normal differentiation and functioning of the conjunctival membranes and cornea [ 2-4 ]. Vitamin A also supports cell growth and differentiation, playing a critical role in the normal formation and maintenance of the heart, lungs, kidneys, and other organs [ 2 ].

The various forms of vitamin A are solubilized into micelles in the intestinal lumen and absorbed by duodenal mucosal cells [ 5 ]. Both retinyl esters and provitamin A carotenoids are converted to retinol, which is oxidized to retinal and then to retinoic acid [ 2 ]. Most of the body's vitamin A is stored in the liver in the form of retinyl esters.

A plasma retinol concentration lower than 0.70 micromoles/L (or 20 micrograms [mcg]/dL) reflects vitamin A inadequacy in a population, and concentrations of 0.70–1.05 micromoles/L could be marginal in some people [ 5 ]. In some studies, high plasma or serum concentrations of some provitamin A carotenoids have been associated with a lower risk of various health outcomes, but these studies have not definitively demonstrated that this relationship is causal.

Vitamin A is the name of a group of fat-soluble retinoids, including retinol, retinal, and retinyl esters [ 1-3 ]. Vitamin A is involved in immune function, vision, reproduction, and cellular communication [ 1 , 4 , 5 ]. Vitamin A is critical for vision as an essential component of rhodopsin, a protein that absorbs light in the retinal receptors, and because it supports the normal differentiation and functioning of the conjunctival membranes and cornea [ 2-4 ]. Vitamin A also supports cell growth and differentiation, playing a critical role in the normal formation and maintenance of the heart, lungs, kidneys, and other organs [ 2 ].

The various forms of vitamin A are solubilized into micelles in the intestinal lumen and absorbed by duodenal mucosal cells [ 5 ]. Both retinyl esters and provitamin A carotenoids are converted to retinol, which is oxidized to retinal and then to retinoic acid [ 2 ]. Most of the body's vitamin A is stored in the liver in the form of retinyl esters.

A plasma retinol concentration lower than 0.70 micromoles/L (or 20 micrograms [mcg]/dL) reflects vitamin A inadequacy in a population, and concentrations of 0.70–1.05 micromoles/L could be marginal in some people [ 5 ]. In some studies, high plasma or serum concentrations of some provitamin A carotenoids have been associated with a lower risk of various health outcomes, but these studies have not definitively demonstrated that this relationship is causal.

This document is a supplement to the Guidance Document for developing and assessing Adverse Outcome Pathways (AOPs). It provides focused and practical instructions for both AOP developers and reviewers and is intended to assist in identifying, organising and evaluating critical information on...

Supplement - definition of supplement by The Free Dictionary


A Supplement to the Journey to the West - Wikipedia

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