Iron and Zinc Supplementation for ADHD

This is the 6th blog post in a series on ADHD. Other posts in this series review non-pharmacologic therapies used to treat ADHD including dietary modification, omega-3s and EEG biofeedback. This post is offered as a concise review of research findings on zinc and iron supplementation in children and adolescents diagnosed with ADHD.

Inconsistent research findings on zinc and iron for symptoms of ADHD

Some children diagnosed with ADHD may have abnormally low plasma zinc levels, which may interfere with optimal information processing and result in difficulties maintaining attention. Findings of studies on zinc in ADHD are inconsistent. In a large 12-week prospective controlled trial 400 children and adolescents randomized to zinc (150 mg/day) experienced significantly more improvement in hyperactivity and impulsivity compared to placebo, but there were no changes in measures of inattention (Bilici et al 2004). A high drop-out rate limited the significance of these findings. In another study adding zinc to a stimulant resulted in greater improvement than stimulant alone. In contrast to these findings a more recent placebo-controlled study failed to show efficacy (Arnold et al 2011). Large prospective studies are needed to replicate these preliminary findings and confirm the optimum dosing of zinc sulfate.

Abnormally low serum ferritin (a molecule in the blood that contains iron) levels may be associated with hyperactivity in non-anemic ADHD children, but not with deficits in cognitive performance. In an open trial non-iron-deficient children given oral iron for 1 month were perceived as less hyperactive and distractible by teachers but not by parents. In a small 12-week randomized placebo-controlled trial non-anemic ADHD children with abnormally low serum ferritin levels randomized to oral iron (ferrous sulfate 80 mg/day) showed progressive improvements in ADHD symptoms over placebo that were comparable to improvements obtained with stimulants. A 2012 systematic review of studies on iron in children diagnosed with ADHD found mixed results in the relationship between serum iron levels and symptom severity, and inconsistent responses of ADHD symptoms to iron supplementation.

Pending more conclusive findings from large well-designed studies it is premature to recommend zinc or iron supplementation to children and adolescents diagnosed with ADHD.