Supplementing multivitamins and iodine to deficient children and learning to play a musical instrument raises the IQ

Raising IQ among school-aged children: Five meta-analyses and a review of randomized controlled trials. John Protzko. Developmental Review, Volume 46, December 2017, Pages 81-101. https://doi.org/10.1016/j.dr.2017.05.001

Highlights
•    There have been 36 RCTs attempting to raise IQ in school-aged children.
•    Nutrient supplementation includes multivitamins, iron, iodine, and zinc.
•    Training includes EF and reasoning training, and learning a musical instrument.
•    We meta-analyze this literature to provide a best-evidence summary to date.
•    Multivitamin & iodine supplementation, and learning a musical instrument, raise IQ.

Abstract: In this paper, we examine nearly every available randomized controlled trial that attempts to raise IQ in children from once they begin kindergarten until pre-adolescence. We use meta-analytic procedures when there are more than three studies employing similar methods, reviewing individual interventions when too few replications are available for a quantitative analysis. All studies included in this synthesis are on non-clinical populations. This yields five fixed-effects meta-analyses on the roles of dietary supplementation with multivitamins, iron, and iodine, as well as executive function training, and learning to play a musical instrument. We find that supplementing a deficient child with multivitamins raises their IQ, supplementing a deficient child with iodine raises their IQ, and learning to play a musical instrument raises a child’s IQ. The role of iron, and executive function training are unreliable in their estimates. We also subject each meta-analytic result to a series of robustness checks. In each meta-analysis, we discuss probable causal mechanisms for how each of these procedures raises intelligence. Though each meta-analysis includes a moderate to small number of studies (< 19 effect sizes), our purpose is to highlight the best available evidence and encourage the continued experimentation in each of these fields.