The effects of oral iron supplementation on cognition in older children and adults: a systematic review and meta-analysis

Systematic review and meta-analysis of randomized controlled trials; participants included children aged 6–18 years, adolescents, and women (including pre-menopausal and pregnant); no men or older adults included; baseline iron status ranged from anaemic and iron-deficient to iron-replete.

Oral iron supplementation using ferrous sulfate, ferrous carbonate, or ferrous fumarate; taken as pills, capsules, or tablets; duration 4 to 29 weeks; dosage not specified.

Iron supplementation improved attention/concentration (SMD 0.59; 95% CI 0.29 to 0.90) with no heterogeneity; improved IQ by about 2.5 points in anaemic baseline participants (95% CI 1.24 to 3.76); no effects on memory, psychomotor skills or scholastic achievement overall; IQ benefit more evident in anaemic groups; results are limited by small, short, methodologically weak trials and potential publication bias; better powered, blinded, independently funded RCTs lasting at least one year across diverse age groups and iron-status categories are needed to confirm and extend these findings.

Small, short-duration trials; methodological weaknesses; potential publication bias; heterogeneity in cognitive tests and populations; limited generalizability (no men or older adults studied); insufficient data on adverse effects and long-term outcomes.