Human Nutrition 3(3+0)

Lesson 20 : Vitamin – A

Effects of vitamin A deficiency

The important deficiency states due to lack of vitamin A in the diet are:

Night blindness: In early stages of vitamin A deficiency, the individual cannot see well in dim light. Difficulty in reading or driving the car in dim light is experienced. In advanced deficiency, the subject cannot see objects in dim light.
Xerosis conjunctivae: The conjunctiva is dry, thickened, wrinkled and pigmented. This is due to the keratinisation of the epithelial cells. The pigmentation gives the conjuctiva a smoky appearance. This condition is extremely common among all age groups in India and other developing countries where the vitamin A intake is low.
Xerosis cornea: When dryness spreads to cornea, it takes on a dull, hazy, lusterless appearance. This is due to the keratinisation of the epithelial tissue covering the cornea
Bitot’s spots: Greyish glistening white plaques formed of desquamated thickened conjunctival epithelium, usually triangular in shape and firmly adhering to the conjunctiva are frequently found in children having other signs of vitamin A deficiency.
Keratomalacia: When xerosis of the conjunctivae and cornea is not treated it may develop into the condition known as ‘Keratomalacia’. Metaplasia and degeneration of the corneal epithelium occur , producing opacities. The cornea becomes vascularized, oedematous and infiltrated with leucocytes. Necrosis, leading to ulceration and bacterial invasion brings about the destruction of the cornea. Blindness often results from corneal scarring or perforation.
Follicular hyperkeratosis( phrynoderma): In the skin of vitamin A deficient animals, follicular keratosis is developed. There is hyperkeratinisation of epithelium lining the hair follicle. The skin becomes rough and dry and papules of varying sizes arising at the site of pilosebaceous follicles are observed. The above condition can be cured by the administration of essential fatty acids and pyridoxine (Gopalan 1947).
Vitamin A and urinary calculus: In animals, vitamin A deficiency has been found to lead to the development of urinary calculus, due to degeneration of the epithelial cells of the urinary tract. However, no such association has been observed between the incidence of vitamin A deficiency and urinary stones in human beings.