Iron and cognition in adolescents Original paper

Iron-deficiency anemia (IDA) is estimated to be the leading cause of disability-adjusted life years (DALYs) lost in adolescents. Iron-containing interventions are commonly integrated into school-based programs that are valued for their perceived improvements in academic performance, but does the evidence indicate that they work?

This systematic review of 50 studies (26 cross-sectional studies and 24 experimental trials) in adolescents evaluated the association between iron status or anemia and measures of cognition or academic performance. It also assessed whether iron-containing interventions improve measures of cognition or academic performance. All of the included studies had an average participant age of 10–19, and 34% of the studies included female participants.

The cross-sectional studies included sample sizes ranging from 30 to 5,398 participants and used various different methods to evaluate nutrition and anemia status (e.g., hemoglobin levels, iron intake). The experimental trials included food-based and iron-only or iron+micronutrient supplementation interventions that lasted 1–14 months. Various types of iron were included at different doses, and sample sizes ranged from 51 to 808 participants.

Learning and cognition outcomes included IQ testing, grades, and specific cognition tests, among others. The included experimental trials were also assessed for risk of bias.

The authors reported the following findings from their analysis:

• Iron status and/or anemia were associated with academic performance in most of the studies. Nearly all iron-containing interventions reported positive findings as well.

• Iron status and/or anemia were not associated with attention and concentration in most studies, although iron-containing interventions reported positive findings more often than not.

• Most of the cross-sectional and experimental studies reported no associations with or changes in intelligence and memory/recall.

• Nearly all supplementation trials had a moderate or high risk of bias.

These results should be interpreted with caution because the outcomes were evaluated with an extremely broad range of assessment methods and interventions and most trials presented a moderate or high risk of bias.