Nature Reviews Disease Primers 3, 17040 (2017)

The spelling of Guatemala has now been corrected in Figure 2. The acknowledgements section has also now been updated to include the following statement: The authors also thank K. Eriksen (MRC Elsie Widdowson Laboratory, Cambridge, UK), S. Moore (MRC Unit The Gambia and Division of Women's Health, King's College London, UK), R. Wessells and S. Hess (Program in International and Community Nutrition, University of California, USA), and G. Kac (Nutritional Epidemiology Observatory, Rio de Janeiro Federal University, Brazil) for providing data from The Gambia, Niger and Brazil to construct Figure 2.