Micronutrients, omega-3 fatty acids and cognitive performance in Indian schoolchildren

In developing countries, approximately 30-40% of school-age children suffer from iodine and iron deficiencies. Poverty and consumption of monotonous diets are underlying causes of inadequate intakes of micronutrients and omega-3 fatty acids and may have severe consequences for children’s cognitive development. Multiple micronutrient interventions have shown to benefit mental performance of children, but a systematic evaluation of the evidence is currently lacking. The omega-3 fatty acid, -linolenic acid (ALA) is converted into docosahexaenoic acid (DHA), a major structural component of the brain, which is important for normal development and maintenance of brain function. At present, it is unclear whether additional intake of omega-3 fatty acids improves cognitive performance in children.The aim of this thesis was to investigate the role of multiple micronutrients and omega-3 fatty acids on cognitive performance in school-age children living in deprived environments, thereby addressing three main research questions.The first query concerned the investigation of the size of effects of multiple micronutrient interventions on different cognitive domains. Findings of our meta-analysis comprising 17 studies in children 5-16 years of age, suggested that multiple micronutrients were beneficial for fluid intelligence (i.e. reasoning abilities) (0.14 SD; 95% CI: -0.02, 0.29) and academic performance (0.30 SD; 95% CI: 0.01, 0.58). Crystallized intelligence (i.e. acquired knowledge) seemed not affected (-0.03 SD; 95% CI: -0.21, 0.15) and for the other cognitive domains data were too limited to draw firm conclusions.Secondly, we examined the role of omega-3 fatty acids on children’s cognitive development, for which a literature review was conducted. Associations between omega-3 fatty acid status or dietary intake and cognitive performance were investigated by cross-sectional analysis using baseline data of a randomized controlled trial in 598 Indian schoolchildren (see below for details). We found no evidence for a beneficial effect of additional intake of omega-3 fatty acids, and of DHA in particular, on cognitive development in school-age children. Neither there was a significant relationship between omega-3 fatty acid status and cognitive performance.Lastly, we studied the effect of different doses of micronutrients and omega-3 fatty acids, and their interaction, on cognitive performance. For that purpose, a randomized controlled trial in 598 Indian schoolchildren aged 6-10 years was conducted from November 2005 until March 2007. Children received either 15% or 100% of the Recommended Dietary Allowance of micronutrients in combination with either a low (140 mg ALA) or high dose (900 mg ALA plus 100 mg DHA) of omega-3 fatty acids for 12 months. Cognitive function was measured at baseline, 6 and 12 months. Our results showed that with some small differential effects on short term memory at 6 months (0.11 SD; 95% CI: 0.01-0.20) and fluid intelligence at 6 months (-0.10 SD; 95% CI: -0.17, -0.03) and 12 months (-0.12 SD; 95% CI: -0.20, -0.04), the high and low dose of micronutrients were as effective for improving retrieval ability, cognitive speediness and overall cognitive performance. Neither there were differences between the omega-3 fatty acid treatments, nor an interaction between micronutrients and omega-3 fatty acids on cognitive outcomes.In conclusion, although multiple micronutrients may benefit intellectual performance of schoolchildren, development of public health guidelines is currently premature. Further investigation on doses and composition of micronutrients would be needed to identify a cost-effective micronutrient supplement to optimize cognitive performance in children. Presently, no evidence exists for a positive effect of omega-3 fatty acids on cognitive performance in healthy children. A final trial using a higher dose and sufficiently long duration would be needed to conclude whether omega-3 fatty acid supplementation improves mental development at school age.