Deep white-matter tracts link docosahexaenoic acid status to cognitive performance in human adolescents.

Docosahexaenoic acid (DHA) is a polyunsaturated fatty acid enriched in neuronal membranes and myelin, linked to cognitive performance. Yet, nutritional interventions show inconsistent cognitive benefits due to a limited understanding of the neural pathways connecting DHA status to human cognition. We studied 99 adolescents selected from both extremes of performance on a national scholastic examination. Participants completed assessments of intellectual ability, provided erythrocyte DHA samples, and underwent multimodal MRI. Using independent component analysis and Bayesian multivariate least absolute shrinkage and selection operator (LASSO) models, we identified brain components jointly associated with DHA and cognition. Across four MRI modalities, a single deep white-matter component consistently emerged as the strongest shared pathway. Tract-resolved analyses highlighted predominant contributions from the fornix and thalamus-temporal fasciculus, with additional subcortical and cortical involvement. These components predicted cognitive measures beyond DHA and other fatty acids, outlining a plausible neural pathway through which a modifiable dietary factor relates to adolescent learning.