Vitamin A

  Vitamin A (or) Antixeropthalmic Vitamin:

History: Elmer MC collum first recognized it as a nutritional factor.Later Holmes isolated it from fish liver oil.

Chemical name: is Retinol.Also called as Anti infective Vitamin due to its role in visual cycle.

 Functions:
1. Plays an important role in vision.Vitamin A aldehyde is essential for the formation of rhodpsin, a factor sensitive to light of low intensity.Deficiency of it leads to impaired adaptation to darkness.
2. It also helps in Tissue growth, helps in maintaining the integrity of the epithelial membranes.
3.  It helps top improve the Immune response hence called as a Anti infective vitamin.It also improve the bone development and helps in remodelling. It is an Antioxidant and Anti cancer agent.
4. It is needed for maintaining a healthy skin. It prevents the dryness of skin and hence helps in keeping the skin moist.
5. It helps in the proper functioning of nerves , brain and thyroid gland.

Deficiency: It leads to Night Blindness- The person can't see in dim light. Conjuctival  xerosis- The conjunctiva becomes dry. Bitot's spot- Greyish scar develops on conjunctiva. Follicular hyperkeratosis- The skin becomes dry and scaly leading to ulcers and bleeding. Keratomalacia - In this condition softening of cornea occurs which leads to complete blindness.

Toxicity : Excess vitamin A leads to toxicity which causes pathogenic changes in bones, periosteal tissues, skin, and mucous membrane.

Sources: Liver, Kidney, Fish, yellow and green leafy veggies and all the dairy products.