• iron absorption
• infant/neonatal nutrition
• inflammation
• infectious disease
• prebiotic

Iron is essential for oxygen transport, generation of energy, synthesis of DNA and multiple enzymatic systems. Iron deficiency impairs these functions and a familiar and important manifestation of advanced iron deficiency is anaemia. Around a quarter of a billion children worldwide are anaemic, and at least half of childhood anaemia is caused in part by a lack of iron; a heavy burden of anaemia is especially present in sub-Saharan Africa and South Asia.1 Iron replenishments, including iron-containing multiple micronutrient powders (MNPs) can be effective treatments to increase haemoglobin. However, despite the use of such agents for many years, the estimated prevalence of anaemia worldwide in preschool children only decreased from 47% to 43% between 1993 and 2011.2 Furthermore, iron replenishments have been associated with adverse events, including infections, intestinal inflammation and diarrhoea in some (but not all) trials. There is a need to make iron treatments both safer and more effective especially in the developing world, and the study in Kenya by Zimmermann and colleagues3 in this issue of Gut addresses these issues.

Iron is needed for growth by humans, and the microbes that colonise and infect us. In particular, pathogenic bacteria in the gut require iron for their virulence, while conversely beneficial …