Associations of adolescents’ diet and meal patterns with school performance in the Northern Finland Birth Cohort 1986: A Mendelian randomisation study

Several observational studies indicate that dietary habits in children and adolescents are associated with school performance. These associations are heavily confounded by socio-economic characteristics, such as household income and parents' educational attainment, amongst other factors. The objective of this study was to explore the association between diet and school performance in adolescents from the Northern Finland Birth Cohort 1986 (NFBC1986).Dietary and school performance data were collected using self-reported questionnaires from adolescents in the NFBC1986 cross-sectional, 16-year follow-up study. In this work we derived exploratory factors for the dietary variables, frequency of skipping main meals and school performance variables, performed genome-wide association studies (GWAS) against these factors to obtain genetic association data and conducted one-sample and two-sample Mendelian randomisation (MR) analyses using individual level data for up to 9220 adolescents in NFBC1986 and GWAS results from external cohorts. We report observational and MR effects of diet on school performance and cognition-related phenotypes.The observational study and the one-sample Mendelian randomisation analysis showed that high fat, salt and sugar (HFSS) consumption was associated with poor school performance in general/science subjects (-0.080, -0.128 to -0.033) and staple food consumption with better school performance in general/science subjects (0.071, 0.024 to 0.119) and physical education (0.065, 0.021 to 0.110). Findings from our two-sample MR analysis identified dietary principal components described best as whole brain bread, wheat, cheese, oat cereal and red wine to be associated with higher educational attainment and other cognition-related phenotypes.Using genetics, we highlighted the potential role of HFSS food consumption and consumption of the components of a staple food diet for school performance. However, further research is required to find conclusive evidence that could support a causal role of diet on school performance.