Question

Mention various diseases caused by deficiency of vitamin ‘A’.

Answer 1

Hint: Vitamin A which is also called retinol is present in all yellow, red and green vegetables like carrots, sweet potatoes and yellow fruits such as mango, papaya. It is also present in cheese, eggs, oily fish, milk and yogurt.

 Complete answer:
Vitamin A is a group of unsaturated compounds which includes retinol, retinal and provitamin A carotenoids. The major form of Vitamin A in food is an ester called retinyl palmitate that converts into retinol which is alcohol chemically in the small intestine.
Vitamin A is found in two forms
>Retinol, which is present in animal foods, is a yellow colored and fat soluble substance.
>The carotenes like alpha-carotene, beta-carotene, gamma-carotene all contain beta-ionone rings.
Functions of Vitamin A
>It is necessary for growth and development.
>Essential for the maintenance of the immune system.
>Improves vision.
>For low light and color vision it is required by the retina of the eye in the form of retinal as it combines with opsin to form rhodopsin (light absorbing molecule).
>Retinoic acid, oxidized form of retinol and important for epithelial and other cells.
Diseases caused by its deficiency
>Night blindness- impaired vision mostly in reduced light.
>Xerophthalmia- dryness in conjunctiva because the lacrimal secreting epithelium is replaced by keratinized one.
>Keratomalacia- debris in plaques and erosion of corneal surface and destruction of cornea.
>Increased risk of ear, urinary tract infections.
>Hyperkeratosis and enamel hypoplasia.

Note:Vitamin A deficiency can be primary and secondary. Primary occurs in children and adults who don’t take optimum amount of Vitamin A from fruits and vegetables. Secondary deficiency is due to malabsorption of lipids, exposure to oxidants like smoke and alcohol.