Deficiency of Vitamin A

Vitamin A encompasses a group of bipolar chemical compounds that are responsible for the normal functioning of the body. Vitamin A performs a wide range of functions, some of which includes gene expression, vision, bones and teeth health, reproduction, red blood cell (RBC) production, cell growth and cell differentiation. It helps the body to fight against infectious diseases by promoting the immune system. Vitamin A can be found in the form of retinol or other retinoids; the former is the usable form found in foods of animal origin; whereas the latter comprises vitamin A related compounds that are commonly used for medicinal purposes.

Vitamin A can be classified into two types based on the source of foods, namely, provitamin A carotenoid and preformed vitamin A. The former type, found in plant sources like fruits (e.g. apricots) and vegetables (e.g. carrots), is not actually vitamin A, but has the potential to convert into usable forms (retinol) in the body. Preformed vitamin A, on the other hand, is found in animal sources such as liver and milk. Let's discuss in brief about the deficiency of Vitamin A.

Deficiency of Vitamin A

Deficiency of vitamin A is of two types, namely, primary and secondary. Primary vitamin A deficiency is caused due to prolonged dietary deficiency, especially observed among people who consume rice as their staple food. This deficiency is often associated with protein deficiency diseases (e.g. marasmus).

Secondary vitamin A deficiency is observed when there is problem in the conversion of provitamin A carotenoid to usable forms, absorption of vitamin A or transportation of vitamin A in the body. Hence, secondary vitamin A deficiency occurs due to certain diseases such as cystic fibrosis, cirrhosis, giardiasis and obstruction of bile duct.

Since vitamin A is responsible for eye health, its deficiency causes various eye symptoms, ranging from reduced night vision to complete blindness. Some of the common eye symptoms include eye inflammation, dry eyes, Bitot's spots (patches in the white part of the eye) and keratomalacia (thinning and ulceration of cornea). Bitot's spots, if diagnosed in the early stages, can be treated by administering medications.

Among the many eye symptoms of vitamin A deficiency, the most important sign is night blindness, which can progress to complete blindness. Every year, thousands of malnourished children lose their sight due to vitamin A deficiency. Night blindness and complete blindness due to vitamin A deficiency can also occur in pregnant women, thus contributing to maternal mortality. As the number of starvation is more in developing countries, vitamin A deficiency complications are more common in these countries.

Another common symptom of vitamin A deficiency is keratinization (accumulation of keratin) of the skin and mucous membrane lining of the digestive and urinary tract. Overall, deficiency of vitamin A reduces the ability of the immune system to fight against diseases, thus increasing the susceptibility of the body towards infection and other health conditions. This is a major reason for the mortality of many malnourished children.

The severity of vitamin A deficiency is more distinct in children as compared to adults. Even a mild deficiency can lead to growth retardation, reduced bone formation and increase chances of developing diseases.