Vitamin A deficiency exists when the chronic failure to eat sufficient amounts of vitamin A or beta-carotene results in levels of blood-serum vitamin A that are below a defined range. Beta-carotene is a form of pre-vitamin A, which is readily converted to vitamin A in the body. Although vitamin A deficiency is found in malnourished, elderly, and chronically sick populations in the United States, it is most prevalent in developing countries.
Vitamin A is critical for vision, bone growth, and normal bodily development. It also plays an active role in supporting the immune system.
The major cause of vitamin A deficiency is a diet that includes few animal sources of pre-formed vitamin A. In addition, iron deficiency can negatively affect vitamin A uptake. Institutionalized children are at particular risk for vitamin A deficiency due to diets low in vitamin A-rich foods.
Night blindness (an abnormal visual adaptation to darkness) is the first symptom of vitamin A deficiency. Prolonged and severe vitamin A deficiency can produce total and irreversible blindness.
Other symptoms include:
Decreased resistance to infections
The diagnosis is based on clinical symptoms and a low level of vitamin A in the blood.
Night blindness is one of the first signs of vitamin A deficiency. Vitamin A deficiency contributes to blindness by making the cornea very dry and damaging the retina and cornea. Approximately 250,000 to 500,000 malnourished children in the developing world go blind each year from a deficiency of vitamin A, approximately half of whom die within a year of becoming blind.
Vitamin A deficiency also diminishes the ability to fight infections and can cause children to die from otherwise non-life threatening illnesses. In countries where children are not immunized, infectious disease like measles have relatively higher fatality rates. Even mild deficiency can be a problem, as it may increase children’s risk of developing respiratory and diarrheal infections, decrease growth rate, slow bone development, and decrease likelihood of survival from serious illness.
The night blindness associated with vitamin A deficiency can be reversed with treatment. Total blindness, however, cannot be treated. Treatment of vitamin A deficiency can be administered in both oral and injectable forms. Food fortification is also useful for improving vitamin A deficiency in large populations. Dietary diversification can also control vitamin A deficiency. The increase in consumption of vitamin A-rich foods of animal origin in addition to fruits and vegetables has beneficial effects on vitamin A deficiency. It is critical to follow your health care practitioner’s recommendations for vitamin A supplementation, as over-consumption can be toxic.
The best sources of vitamin A are eggs, milk, butter, liver, and fish, such as herring, sardines, and tuna. Plants do not contain vitamin A, but they do contain beta-carotene and other carotenoids which are converted to vitamin A in the body. The best sources of beta-carotene are dark-green, orange, and yellow fruits and vegetables such as spinach, carrots, oranges, and sweet potatoes.