Effects of increased hemoglobin on child growth, development, and disease: a systematic review and meta-analysis.

In children under 5, a hemoglobin (Hb) cutoff of 11 g/dL is recommended by the World Health Organization to define anemia, yet few studies have examined whether this cut point accurately coincides with negative functional consequences. This systematic review and meta-analysis of iron intervention and observational studies aimed to clarify the consequences of low Hb concentration in children under age 5 years on growth, development, and chronic disease (functional outcomes) across the full range of Hb values. A literature search returned 5049 studies; of these, 56 intervention and 20 observational studies fit the inclusion criteria.