National-level data on iron deficiency is not available for most countries and many rely on the prevalence of anemia as a proxy estimate, assuming that approximately 50% of anemia cases are caused by iron deficiency. Anemia, however, has multiple causal factors and the risk attributable to any one cause will depend on its relative importance in a population in relation to other causes. The present review summarizes current estimates on the prevalence of iron deficiency and anemia in children younger than 2 years and evaluates the strengths and weaknesses of currently available indicators of iron deficiency in children. Anemia prevalence is insufficient to estimate the prevalence of iron deficiency in children younger than 2 years. The methods widely used to assess iron deficiency at the population level rely on venous blood samples and are complicated and costly to implement.

Micronutrient deficiency remains a major public health problem in many countries worldwide with important consequences for the health of the population and child growth and development. The objective of this article is to review information that should be taken into consideration in identifying the need for and in designing micronutrient programs. We review information that could be used to identify nutritional need, including the prevalence of deficiency and evidence of inadequate dietary intake as well as potential data sources and some strengths and weakness of such data for program decision-making. We also review factors that might modify the potential impact of programs and that should therefore be taken into consideration in their design. For example, such factors may include access to formal and informal health systems, quality of health provider training, and behavior change communication and complementary or overlapping interventions. Nationally representative data on micronutrient deficiencies and dietary intake are most useful for identifying unmet needs. Although the burden of micronutrient deficiencies lies in low-income countries, few have detailed information on specific deficiencies beyond anemia, and nationally representative dietary intake data are scarce. Nationally representative data may still mask considerable within-country variability by geographic, economic, or ethnic group. Some efforts designed to promote coordination in nutrition programming within countries utilizing information on prevalence, intake, and program coverage and utilization are also reviewed. Improving the quality of such data and ensuring continual updates are vital to guide decision making and to ensure that programs can appropriately respond to needs.

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