 This paper examined the effects of iron deficiency in women of child-bearing age on their cognition, mental health and fatigue. The authors found that three studies showed poorer cognition and mental health scores and increased fatigue with iron deficiency at baseline. However, seven studies reported an improvement in cognitive test scores after iron supplementation. These studies also showed a significant improvement in arithmetic scores after iron supplementation, P less than 0.01. Despite this, the evidence base is limited due to poor study quality and heterogeneity across studies. More high-quality studies using consistent measures are needed before any conclusive statements can be made. This article was authored by Alesha J. Gregg, Amanda J. Patterson, Claire E. Collins and others.