Role in vision careThere are four kinds of photo pigments contained in human retina and they can store vitamin A compounds.
The retinol form has a special role in vision cycle. Rhodopsin, one of the retinal pigments is contained in rod cells of the retina. Rhodopsin is needed for rod cells to detect small amounts of light and to see black and white. Deficiency leads to night blindness by inhibiting the reformation of rhodopsin.
Skin care and immunity careIn the retinoic acid form, Vitamin A, plays an important role in gene transcription. It has active function in maintaining normal skin health and is a ingredient in skin care products. Several immunity connected activities are stimulated by it . It primes up the white blood cells to increase the responses to antigens and has anti-viral activity. It has a positive role in preventing shrinkage of thymus gland.
Care in food habits to prevent vitamin A deficiencyVitamin A deficiency can occur in adults and in children. Lack of care in consuming adequate quantities of the vitamin’s source foods can lead to primary or secondary levels of deficiency. In new born, early weaning can lead to its deficiency unless care is taken to supplement it. In developing countries, the high incidence of blindness, viral infections, and child mortality due lack of care in food habits leading to its deficiency. In its deficiency the health of the skin, the elasticity of skin, hair, eyes, and immune system are affected. Further poor appetite, bone development abnormalities, and growth retardation are associated with insufficient intake of vitamin A. Hyperkeratosis of skin, a goose pimple like look of the skin caused by excessive production of keratin that blocks hair follicles. The skin becoming dry, scaly and rough and hair is lost.
With proper supplementation and skin care efforts normalcy of the skin can be achieved. Night blindness and total loss of vision can occur in prolonged deficiency by setting in of the condition called Xerophthalmia where in cornea of the eye and conjunctiva undergo change.
ToxicityBeing fat soluble, vitamin A is absorbed and stored in body when in excess.
This excess presence can cause nausea, jaundice, pains and general physical and mental debility. In-take in the form of fruits and vegetables does not usually cause toxicity.
Supplements in the form of tablets and animal sources have to monitored and care must be taken to avoid overdose.