by Agnes Naswa

Created on: December 04, 2009

Retinol- Vitamin A.

Vitamins essentially are organic naturally occurring substances which the human body requires in minute amounts for its normal metabolic process, but which it cannot synthesize for itself in sufficient quanta. Retinol is a vitamin that is found in foods of animal origin. Animals obtain it from its precursor or Pro-vitamin- the orange pigment, carotene.

The conversion of Beta-Carotene into retinol in the human body is incomplete and involves very considerable loses. This process takes place to a very large extent, if not entirely in the lining of the small intestine. The absorption of both retinol and retinol is facilitated by fats and bile salts as the Vitamin is fat-soluble as opposed to being water soluble. It is believed that retinol has an active role in the metabolism of all human cells, but the precise manner in which it behaves is not fully comprehended in biochemical terms except in the retina, hence the name retinol.

The Primary dietary sources of retinol are milk, cheese, butter, liver, egg yolk and some fatty fish like the Nile perch . The liver oils of fish like cod are the richest natural sources of Vitamin A but these are often used as dietary supplements as opposed to being food proper. Carotene or Pro-Vitamin A is found in abundance among plant foods. It is found chiefly in green vegetables in association with chlorophyll, so that the green outer leaves of vegetables like collards and cabbages are good sources, while the white inner leaves of cabbages contain little or no carotene.

Other noteworthy sources are yellow and red fruits and vegetables like carrots. Vegetable oils are devoid of retinol except for red palm oil which is extensively produced in West Africa, Indonesia and Brazil. This oil is extremely rich in carotene; retinol is often added artificially to margarine to the same concentration as that of good quality summer butter.

Both retinol and carotene are stable to ordinary cooking methods, though miniscule loses might occur at temperatures above100 Celsius for example when butter is used for stir frying. The Recommended Daily Allowance or intakes of retinol are 300 mg for infants and young children, 500-600 mg for children of 9 to 15 years, 750 mg for adolescents and adults and 1,200 mg for lactating women. Therapeutically Thiamin is invaluable in the treatment of Xerophtalmia, Keratomalacia and of Night Blindness when this is due to dietary failure. It can also be administered to malnourished people who show evidence of follicular Keratosis. The above conditions are prevalent mainly in underdeveloped countries of Asia, Africa and South America.

There is the clinical impression that retinol improves children's growth and well-being. The prescription of Vitamin A for the prevention of the common cold and other conditions in people taking a mixed diet is not justified by any known reliable clinical evidence. Retinol is an essential component of the pigment rhodopsin (visual purple) on which vision in dim light depends. Lack of retinol may result in the impairment of "dark adaptation" measurable by an adoptometer. This condition is common ion impoverished people living in underdeveloped countries. It can also occur in the malabsorption syndrome in rich countries. In such cases it responds excellently to retinol. After all is said and done though just ensure that you eat a fully well balanced diet consisting of Proteins, Vitamins and carbohydrates.

Learn more about this author, Agnes Naswa.
Click here to send this author comments or questions.