Effectiveness of vitamin A supplementation in the control of young child morbidity and mortality in developing countries. Revised ed.
Researchers affiliated with the International Nutrition Program at the University of Toronto reviewed 20 trials of vitamin A and morbidity and 10 trials of vitamin A and young child mortality to determine the effectiveness of vitamin A supplementation on reducing mortality and morbidity in children from developing countries. All the populations were characterized by general poverty, high prevalence of stunting, and clinical manifestations of vitamin A deficiency sufficiently prevalent to be considered a public health problem. The analysis using the random effect model confirmed that vitamin A supplementation does indeed reduce mortality rates in young children (by about 23%) (relative risk = 0.77, confidence interval = 0.68-0.88; p < 0.001). The 10 trials reported reductions in mortality associated with vitamin A supplementation ranging from 0 to 50%. Vitamin A supplementation reduced mortality rates regardless of gender and age between 6 months and 5 years. It had clear effects on mortality linked to diarrhea and measles. It apparently had no effect on mortality linked to respiratory infections and malaria. None of the mortality studies included children with biochemical evidence of vitamin A depletion with associated evidence of at least a low prevalence of xerophthalmia. The effect of vitamin A supplementation on morbidity is less clear than its effect on mortality. Vitamin A supplementation does not appear to improve general morbidity but does have a beneficial effect on severe morbidity. In the case of measles, the evidence suggests that, even after the onset of infection, vitamin A supplementation can improve the course of the episode and the case fatality rate. In conclusion, vitamin A probably has more of an effect on the processes linked to response to infection than to those linked to resistance to infection.