Vitamin A deficiency is a major public health problem affecting an estimated 190 million preschool-age children, mostly from the World Health Organization (WHO) regions of Africa and South-East Asia
- infants and children have increased vitamin A requirements to promote rapid growth and to help combat infections. Inadequate intakes of vitamin A at this age could lead to vitamin A deficiency, which, when severe, may cause visual impairment (night blindness) or increase the risk of illness and mortality from childhood infections such as measles and those causing diarrhoea
- vitamin A deficiency alone is responsible for almost 6% of child deaths under the age of 5 years in Africa and 8% in South-East Asia
- vitamin A supplementation in children 6-59 months of age living in developing countries is associated with a reduced risk of all-cause mortality and a reduced incidence of diarrhoea
- mechanisms by which vitamin A reduces mortality are not fully understood, and it is not clear whether its action is mediated through the correction of underlying deficiencies or through adjuvant therapeutic effects. Vitamin A supplementation may improve gut integrity and therefore decrease the severity of some diarrhoeal episodes
- role of vitamin A in innate and adaptive immunity may also include reducing susceptibility to and/or severity of other infections
Certain infections, most notably measles in Africa, greatly increase demand for vitamin A, so that supplements improve clinical outcome and survival. Vitamin A deficiency interferes with the normal immune response to the measles virus and HIV, and reduces the response to parasitic infection.
WHO conclude "..Supplements appear to be of less benefit in respiratory tract infection than in some other types of infection. However, the cumulative evidence suggests that supplementation may limit the progression of both respiratory and gastrointestinal infection..." (2)
Reference:
- Bates, C.J. (1995) Vitamin A The Lancet 345; 31-35
- WHO (2011). Vitamin A supplementation in infants and children 6-59 months of age.