Vitamin A Flashcards
What is vitamin A?
Vitamin A is a generic term that describes retinol and related structures and the pro-vitamin A carotenoids
Retinoids include retinol, retinal and retinoids acid
Carotenoids are plant pigments that help plants absorb light energy for photosynthesis and also act as antioxidants
How do we measure activity of retinol?
Activity of retinol is described as retinol equivalents (RE)
1 microgram of RE = 1 microgram retinol
1 microgram of RE = 6 microgram of beta-carotene
1 microgram of RE = 12 microgram of other carotenoids
What are the functions of Vitamin A?
Maintains healthy corneas, epithelial cells and mucous membranes of the eye, aiding in reproduction and growth, improving the health of epithelial tissues and skin through protein synthesis and cell differentiation and providing immunity
How is vitamin A important for the visual cycle?
Vitamin A is a key component of the visual cycle
11-cis retinal is component of chromophore found in two types of light receptors - rod cells (low light intensity) and cone cells (higher light intensity and colour)
How is vitamin A important for visual health?
Vitamin A is involved in the health of epithelial cell
Makes retinoic acid that is needed to keep eye most, first sign of vit A deficiency is dry eyes / bitots spot
What is vitamin A deficiency?
If you develop the inability to see in dim light you make have vitamin A deficiency - affects 1% of children aged 6months - 6years old
Vitamin A deficiency can result in vision problems, most common cause of preventable blindness however if not picked up can lead to permanent and irreversible blindness
Can also result in keratinisation - changes in epithelial cells, results in rough, dry and scaly skin
Risk factor for severe measles
What are some food sources for Vitamin A?
Vitamin A is found in retinoids - liver is the richest source, also milk, butter, cheese, egg yolk, some fatty fish
Also found in carotenoids - low income countries, dark green leafy vegetables, carrots, pumpkins, mangoes and papaya
Golden rice
How is vitamin A digested and absorbed?
Vitamin A is a fat soluble vitamin hence integrated/taken into chylomicron which go into the lymph
Stored associated with fat primarily in the liver
What is vitamin A toxicity?
Vitamin A and beta-carotene toxicity can occur when concentrated amounts of the pre-formed vitamin A from animal foods or supplements. Symptoms include birth defects, death (acute), chronic effects and discolouration of skin
