Though iron deficiency anemia (IDA) remains a common cause of anemia in young children, even more common is the prevalence of nonanemic iron deficiency (NAID). For decades, there has been concern for irreversible adverse effects of chronic iron deficiency with or without anemia on cognitive function in children. In a landmark observational study begun in the early 1980s, Lozoff and colleagues studied 185 Costa Rican infants from a low-resource setting and followed them into adulthood. They reported both initial and long-term cognitive inferiority in the subjects with chronic iron deficiency with or without anemia.1–4  The report by Gingoyon et al in this issue of Pediatrics readdresses these concerns in a high-resource setting, using a select group of infants from a multisite, longitudinal cohort study, TARGet Kids!, based in Toronto, Canada.5 Healthy children were recruited at primary care visits between 12 and 40 months of age and...

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