A meta-analysis of nutrition interventions on mental development of children under-two in low- and middle-income countries

Interventions to improve nutritional status of young children in low- and middle-income countries (LMIC) may have the added benefit of improving their mental and motor development. This meta-analysis updates and goes beyond previous ones by answering two important questions: (1) do prenatal and postnatal nutritional inputs improve mental development, and (2) are effects on mental development associated with two theoretically interesting mediators namely physical growth and motor development? The meta-analysis of articles on Medline, PsycINFO, Global Health and Embase was limited to randomized trials in LMICs, with mental development of children from birth to age two years as an outcome. The initial yield of 2689 studies was reduced to 33; 12 received a global quality rating of strong. Of the 10 prenatal and 23 postnatal nutrition interventions, the majority used zinc, iron/folic acid, vitamin A or multiple micronutrients, with a few evaluating macronutrients. The weighted mean effect size, Cohen's d (95% CI) for prenatal and postnatal nutrition interventions on mental development was 0.042 (-0.0084, 0.092) and 0.076 (0.019, 0.13), respectively. Postnatal supplements consisting of macronutrients yielded an effect size d (95% CI) of 0.14 (0.0067, 0.27), multiple micronutrients 0.082 (-0.012, 0.18) and single micronutrients 0.058 (-0.0015, 0.12). Motor development, but not growth status, effect sizes were significantly associated with mental development in postnatal interventions. In summary, nutrition interventions had small effects on mental development. Future studies might have greater effect if they addressed macronutrient deficiencies combined with child stimulation and hygiene and sanitation interventions.