Neurological effects of iron supplementation in infancy: finding the balance between health and harm in iron-replete infants.

Iron mediates many biochemical processes in neural networks that proliferate during brain development. Insufficient iron causes irreversible neurodevelopmental deficits, and most high-income countries recommend that infants older than 4-6 months receive additional iron via food fortification or supplementation to prevent iron-deficiency anaemia. Now that the prevalence of iron-deficiency anaemia in children has decreased to less than 10% in most developed countries, concerns that the recommended intakes far exceed those required to prevent iron-deficiency anaemia have been raised, and emerging evidence suggests that iron overexposure could be linked to adverse outcomes later in life. In this Viewpoint, we discuss the importance of iron for neurodevelopment, investigate the biochemical markers used to assess iron stores, summarise the disparity in public health policies among high-income countries, and discuss the potential association between iron overexposure and adverse neurological outcomes later in life. We present a case for new studies to establish the optimal amount of iron that both prevents deficiency and reduces the potential risk of long-term negative health outcomes.