Vitamin A deficiency: A lack of vitamin A.

Vitamin A deficiency (VAD) occurs where diets contain insufficient vitamin A for meeting the needs associated with growth and development, physiological functions, and periods of added stress due to illness. Infections such as measles may precipitate a child into clinical VAD. In VAD areas, women of childbearing age are at high risk of VAD and its consequences because of increased vitamin A requirements during pregnancy and lactation. Their newborns having been vitamin A depleted require vitamin A supplements. Otherwise, following their initial 4-6 months of nursing they are likely to develop VAD.

Vitamin A deficiency (VAD) is a significant public health problem in over 75 countries. The children of developing countries suffer most from this condition, which is largely preventable. It is estimated that up to 230 million children are at risk of VAD and over one million VAD-associated childhood deaths occur annually. The effects of VAD include the following:

• 14 million pre-school children have some eye damage due to VAD;
• 350 000 (or more) pre-school children become partially or totally blind every year from VAD;
• About 60% of these children die within a few months of going blind;
• VAD is associated with an increase in the severity of infections, particularly measles and diarrheal disease;
• Through synergism with measles infection, VAD contributes to the estimated 1.1 million childhood deaths from measles every year;
• Half of all childhood corneal blindness in developing countries is caused by vitamin A deficiency, and half of that is from added measles infection.

Improving the vitamin A status of deficient children and treating cases of measles with vitamin A can reduce childhood morbidity and mortality substantially. Taking into account the results of eight randomized controlled community supplementation trials, one report concluded that improving the vitamin A status of young children reduced mortality rates by about 23%. Studies from Ghana and Brazil have also indicated that vitamin A supplementation was associated with a decrease in disease severity. In three studies of children hospitalized with measles, vitamin A supplementation reduced the death rate by about 60%.