in the present analysis based on a reassessment of existing and new supplementation trials. Furthermore, we quantified the proportion of the population who are vitamin A or zinc deficient instead of classing whole countries as exposed or non-exposed. The evolving epidemiology of exposure to micronutrient deficiency and the subsequent health effects suggests a need to systematically reconsider most single nutrient supplementation for children in preventive strategies to lower child mortality, as suggested by the 2000 comparative risk assessment and later analyses. 10 Therapeutic zinc supplementation in health-care settings is feasible, as is iron supplementation during pregnancy.174–179 Our findings support the need for strengthened policy about promotion of optimal breastfeeding practices and nutritional programmes that improve child growth. The estimated number of child deaths caused by underweight has also changed substantially over successive studies: in GBD 1990 it was estimated to be 5·9 million deaths in 1990,180 in the comparative risk assessment study for 2000 as 3·7 million deaths,7 and 1·9 million deaths in 2004.10 In GBD 2010 we estimated 2·3 million deaths for 1990 and 0·9 million deaths for 2010.
