It wasn't until 1913 that vitamin A was deemed necessary for growth. This discovery was found on young animals, as they were fed a diet restricted in natural fats. Of course they animals became unhealthy, established a poor immune system, an inability to grow, inflamed and infected eyes. Don't worry about these animals because they were fed cod liver oil and butterfat to quickly relieve them. This is when vitamin A became known as 'Anti-infective Vitamin' and gained a lot of recognition as the vitamin that enhances the immune system.
The primary deficiency in vitamin A may be from inadequate dietary intake, and the second reason is due to some type of interference with the absorption or the transportation or even the storage of vitamin A in the liver. Let's break this down into more specific causes:
* liver disease
* insufficient bile acid causing malabsorption
* zinc deficiency
* abetalipoproteinemia (interference with absorption of fats and fat soluble vitamins from a autosomal recessive disorder).
With vitamin A deficiency, the immune system becomes weakened. An effective response for antibodies becomes impaired, which can lower the levels of helper T-cells and the respiratory and gastrointestinal mucosal linings can experience alterations. This allows a person to be more susceptible to infectious diseases. Chicken pox, measles, pneumonia, and respiratory cytial virus are a few known infectious diseases connected to vitamin A deficiency. The eye disease associated with vitamin A deficiency is xerophthalmia. A prolonged deficiency results in night blindness, increased rate of infections and white bumps on elbows and/or goose bump appearance in hair follicles on the back of the upper arm.
Your body uses vitamin A for...
Growth & Development - it has a role in glycoprotein synthesis in which may control gene expression and differentiation
Reproduction - beta carotene (a conversion of vitamin A) has an effect on fertility.
Immune System - is essential for the immune system to function properly. In 1932, many studies showed that vitamin A supplementation reduced infant mortality by 50% in patients with measles.
Skin Disorders - in the late 1930's, dermatologists introduced vitamin A therapy like acne, psoriasis, itchthosis, Darier's disease, lichen plantus and others. This therapy has become less popular over time, as many neglect to safely dose under a practitioner's guidance and toxicity became an issue.
Good sources of vitamin A are:
Olson R, ed., Nutrition Reviews' Present Knowledge in Nutrition, 6th Edition. Nutrition Foundation, Washington, DC, 1989, pp. 96-107.
Underwood B, Vitamin A in animal and human nutrition. The Retinoids, Vol 1, Sporn M, Roberts A, and Goodman S (eds.). Academic Press, Orlando, FL, 1984, Chapter 6, pp. 282-392.
Bendich A, Beta-carotene and the immune response. Proc Nutr Soc 50, 263-274 1991.