Purpose of review: Iron deficiency is the most common nutritional disorder affecting about 20-25% of the world's population, predominantly children and women. There is emerging evidence that depletion of iron stores may have adverse consequences for adults even in the absence of anaemia. This raises issues about the most appropriate method of assessing iron status.
Recent findings: Although the effects of iron-deficiency anaemia are well characterized, emerging evidence suggests that iron deficiency without anaemia can have negative consequences in adults, particularly for neurocognitive outcomes. Iron deficiency is more likely in women of reproductive age because of menstrual blood loss. However, extremes of blood loss such as regular blood donation, diets of low bioavailability and the challenges of pregnancy all markedly increase the risk of iron deficiency. In addition, the physiological changes in pregnancy affect the normal reference ranges used in laboratory assessment. The use of haemoglobin as a marker of iron deficiency is limited by its low specificity and sensitivity and although the use of alternative biomarkers is becoming more common, interpreting results in conditions of chronic inflammation, including that associated with increased adiposity, needs more investigation.
Summary: By understanding the physiology of iron metabolism alongside the limitations and interpretation of biomarkers of iron deficiency, clinicians and nutritionists are better equipped to identify changes in iron balance and to further investigate the functional outcomes of iron deficiency.