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Throughout Africa, India, the Philippines, and much of South America, vitamin A deficiency causes devastating symptoms. Every year, approximately 250,000 children under five go blind because their diets do not provide enough vitamin A. And approximately 700,000 children die of diarrhea or measles which their bodies cannot fight because of a lack of vitamin A.
Primary and secondary vitamin A deficiency. Vitamin A deficiency can be primary or secondary. Primary vitamin A deficiency occurs when the diet does not provide enough retinyl palmitate (from certain kinds of liver and dairy products) or beta-carotene (from orange, yellow, and dark green vegetables). Primary vitamin A deficiency is rare in the industrialized countries but not unusual in the developing world.
Secondary vitamin A deficiency results from an inability to absorb vitamin A, usually because of a failure of the liver to produce bile salts, or an inflammatory bowel disease, or because of alcoholism or exposure to cigarette smoke. Secondary vitamin A deficiency is rare in the developing world but not unusual in relatively wealthy countries where most people have access to "good" nutrition.
Loss of night vision. In adults, either kind of vitamin A deficiency usually shows up first as night blindness. This occurs because the retina needs vitamin A to detect low levels of light. The vitamin deficiency may cause partial loss of vision rather than absolute blindness If the deficiency is not corrected, even more vitamin A deficiency symptoms affect the eyes.
The tear ducts literally dry up. They are replaced by tough scar tissue. When the eyes are not cleansed and lubricated by tears, then infections can take hold in the conjunctiva, or "whites," of the eyes. The cornea can erode and total blindness may result.
Problems not limited to the eyes. The symptoms of vitamin A deficiency don't stop there. There can also be destruction of the lining of the bladder. This leads to devastating bladder infections. White lumps can form at the base of hair follicles before the hair falls out. Tough areas of scar tissue can form in the lungs, and the central nervous system becomes more vulnerable to attack by meningitis infections.
Fortunately, it's not hard to treat severe vitamin A deficiency. A single dose of 100,000 to 400,000 IU of vitamin A, given under the supervision of a trained health worker, can stop blindness and the other changes caused by deficiency, if the vitamin is given soon enough.
Less severe symptoms of less severe deficiency. In Australia, Canada, New Zealand, the UK, and the USA, vitamin A deficiency is usually secondary deficiency, and much less severe. The most common symptom of moderate vitamin A deficiency are those associated with iron-deficiency anemia, such as restless legs syndrome, fatigue, weakness, and lightening of the skin. Iron deficiency can also cause unusual food cravings, such as crunching ice. Some people who are deficient in vitamin A will also notice slight problems seeing at night or adjusting to low light.
You should never guess whether you have iron deficiency anemia. A simple and inexpensive blood test will tell for sure, and if the test tells you that you are deficient in iron, you can take a supplement. For the iron supplement to work, however, you will also need vitamin A, at least 5,000 IU a day, taken indefinitely even after your iron levels go back to normal.
Black RE et al., Maternal and child undernutrition: global and regional exposures and health consequences, The Lancet, 2008, 371(9608), p. 253.
J S Rahi, S Sripathi, C E Gilbert, A Foster. Childhood blindness due to vitamin A deficiency in India: regional variations. Archives of Disease in Childhood. 72: 330-333, 1995.