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Vitamine A

Constituents

A1 = retinol

A2 = dehydroretinol

carotene α

carotene β

carotene γ

Provenience

main: - animal: milk, eggs and animal liver - vegetable: carrots

Action

Retinol and dehydroretinol are alcohols. They are transformed by the enzyme alcoholdeshydrogenase into the corresponding aldehydes, retinal and dehydroretinal. The carotenes are split in two, and oxidized into retinal by the enzyme β carotene-dioxygenase .

retinal

These aldehydes are the true active ingredients that - ensure growth - maintain the mucous membranes - nourish the skin - form the retinal pigment - make mature the spermatozoa

Estimated average needs

adult (non-alcoholic): 1.5 mg / d child: 0.45-1.5 mg / d pregnant woman: 1.8 mg / d breastfeeding woman: 2.4 mg / d

Deficiency

- difficulty to see in the darkness - inflammation, then loss of the eye - "toad skin" - respiratory infections - urinary stones - male sterility