Vitamin A, zinc, iodine, iron and folate are the focus of Dr. Robert Black’s talk on the global disease burden related to micronutrient deficiencies. How effective is micronutrient supplementation in addressing these deficiencies? Black outlines the current global status and examines this in light of clinical trial data. A key point that affects the outcomes of supplementation trials is the type of outcome measure used to calculate the results. Black points out the relevance of cause-specific mortality when evaluating the efficacy of micronutrient supplements. For example, diarrhea-related and pneumonia-related mortality are relevant to zinc supplementation, whereas neural tube defects are relevant to folate supplementation.Nevertheless, there is some controversy in the clinical findings as illustrated by meta-analyses of iron supplementation trials. Despite the importance of iron for cognitive function, iron supplementation only showed benefits on motor development but not mental development. Additional studies are needed in order to identify the optimal timing and duration of micronutrient supplements in order to alleviate the global burden of deficiency in infants and young children.