Neurodevelopmental growth is rapid during infancy, significantly influenced by factors such as parental interaction, environment, socioeconomic status, and nutrition. A restrictive diet has been linked to early neurodevelopmental problems in both animal and human studies. However, analyzing dietary patterns at a single time point is insufficient, as infant diets change over time. This study hypothesized that early childhood dietary patterns influence later neurodevelopment and aimed to investigate the effect of diverse weaning foods and diet patterns at multiple time points on six developmental domains in 6-year-old children, controlling for socioeconomic status. The research aimed to inform guidelines for caregivers regarding optimal children's eating habits.

Existing research highlights the crucial role of early nutrition in brain development. Studies have shown that an enriched environment, including diverse nutritional support, positively impacts neurogenesis and neural circuit development. Conversely, restrictive diets or diets lacking in variety have been linked to delayed neurodevelopmental outcomes. Animal studies, particularly those involving rats fed soft diets, have demonstrated negative effects on hippocampal cell proliferation. Human studies in rural China have also found a correlation between low dietary diversity and delayed neurodevelopment. However, a limitation in previous research has been the focus on single time-point dietary assessments, neglecting the dynamic nature of infant feeding practices.

This administrative observational study merged data from the Korean National Health Insurance Service (NHIS) and the National Health Screening Program for Infants and Children (NHSPIC). The study population comprised 2,395,966 Korean children born between 2008 and 2012, with 133,243 meeting the inclusion criteria after exclusions for various factors (e.g., death, low birth weight, prematurity, perinatal diseases). Dietary information from NHSPIC questionnaires (rounds 1-4, ages 4-36 months) was used. Polytomous Latent Class Analysis (poLCA) identified four dietary clusters based on factors including milk type, weaning food initiation time, ingredient diversity, and meal frequency. Neurodevelopmental outcomes at age 6 were assessed using the Korean Developmental Screening Test (K-DST), encompassing six domains (gross motor, fine motor, cognition, language, sociality, self-care). Multivariate logistic regression analyzed the association between dietary clusters and unfavorable K-DST outcomes, adjusting for covariates such as sex, region of birth, economic status, birth weight, head circumference, perinatal conditions, and comorbidities. The poLCA package (version 1.6.0.1) in R (version 4.1.3) and SAS version 9.4 were used for statistical analysis.

The study identified four dietary clusters: a control cluster (53.4%) with high breast milk feeding and diverse dietary patterns at age 1; cluster 1 (36.0%) with a skewed dietary pattern at age 1; cluster 2 (6.6%) with diverse patterns at age 1 but primarily formula feeding at 4 months; and cluster 3 (4.0%) with reduced diversity and formula feeding. Compared to the control cluster, adjusted odds ratios (aORs) for unfavorable K-DST outcomes were significantly higher in clusters 1 (aOR 1.209, 95% CI 1.156–1.266), 2 (aOR 1.418, 95% CI 1.312–1.532), and 3 (aOR 1.741, 95% CI 1.593–1.903). These associations were consistent across all six K-DST domains. Cluster 3, characterized by the lowest dietary diversity and late introduction of complementary foods, had the highest risk of unfavorable neurodevelopmental outcomes. Baseline characteristics showed differences among clusters in birth region and economic status, but not significantly in birth weight or head circumference.

The findings support the hypothesis that dietary patterns during infancy and early childhood are associated with neurodevelopmental outcomes at age 6. The control cluster, aligning with recommended dietary guidelines (breastfeeding, diverse complementary foods introduced at 4-6 months), showed the lowest risk of unfavorable K-DST results. Deviations from these guidelines, particularly in clusters 1, 2, and 3, were associated with increased risk. Potential mechanisms include the impact of dietary diversity on creating an enriched environment, the provision of essential nutrients for brain development, and the influence of diet on the gut microbiome, which modulates brain function. This study provides strong evidence for the importance of diverse and timely introduction of complementary foods during infancy for optimal neurodevelopment.

This large-scale longitudinal study demonstrates a strong association between diverse weaning food intake and timely introduction of complementary foods with favorable neurodevelopmental outcomes at age 6. The findings highlight the significance of adhering to recommended dietary guidelines for infants and young children. Future research could explore the specific nutrient profiles and gut microbiome compositions associated with these dietary patterns to further elucidate the underlying mechanisms. Investigating potential mediating factors such as parental education and family environment would also strengthen the evidence base.

The study relied on caregiver-reported dietary data, potentially introducing recall bias. Assessment of neurodevelopment using the K-DST at a single time point may not capture the full spectrum of developmental trajectories. The dataset did not include information on parental education level, family structure, and other potentially influential environmental factors, which could be considered as limitations of the current study.