Vitamin A is key for good Vision, a healthy immune system, and cell growth. There are two types of vitamin A. This entry is primarily about the active form of vitamin A -- retinoids -- that comes from animal products. Beta-carotene (Provitamin)is among the second type of vitamin A, which comes from plants.
- Animal sources are liver oil, butter, milk , cheese & egg yolk.
- Plant sources in the form of Provitamin are tomatoes, carrots, yellow & green vegetables , spinach, fruits such as mangoes , papaya & sweet potatoes.
- Adult : 3000-5000IU
- During pregnancy & lactation : 6000-8000IU
- Children : 2000-3000IU
- Infants: 1500IU
1IU = 0.3microgm of Retinol
=0.6microgrm of beta-carotene
Absorption, storage & Transport
The liver is the major storage site ofvitamin A. For storage, the retinol will be transported from the hepatocytes to the stellate cells and converted back to retinyl esters, the storage form of vitamin A. If vitamin A is needed to be released into circulation, retinol will combine with
etinol binding protein (RBP).
Functions of Vitamin A
- Role in vision
- Help in maintaining the integrity of epithelial tissues
- It accelerates the normal function of bones & teeth.
- It acts as growth promoting factor in childhood.
- 13-cis-Retinoic acid is used in the treatment of severe acne .
- Night blindness (Nyctalopia)
- Dry eye (Xeropthalmia)
- Destruction of cornea (keratomalacia)
- Defective teeth formation
- Bitot's spots are seen.
- Alteration of skin & mucosal membrane
- Hepatic dysfunction
- Loss of weight
- Falling of hair
- Peeling of skin about the mouth
- Headache , drowsiness & anorexia.