Eating the rainbow early: Food diversity in infancy and the risk of atopic dermatitis in 267,935 Korean children.

BACKGROUND: Early introduction of diverse foods may be associated with a lower risk of atopic dermatitis (AD), yet the evidence remains limited by small cohort sizes and subjective recall bias. We aimed to examine this association using a large, nationwide population-based cohort. METHODS: This cohort study utilized the Korean National Health Insurance Service database (267,935 infants born 2009-2010). Food diversity at 12 months (six food groups) was categorized as low (0-2), moderate (3-4), or high (5-6). The primary outcome was incident AD, ascertained from the index date through the end of follow-up based on ≥2 diagnostic claims and ≥2 topical corticosteroid prescriptions. We minimized reverse causation by strictly excluding infants with prior AD. Cox models were employed, adjusting for clinical covariates and, crucially, maternal allergic history due to its significant influence on infant feeding practices. RESULTS: Among the 267,935 eligible infants, 20,362 (7.6%) were in the low, 95,241 (35.5%) in the moderate, and 152,331 (56.8%) in the high diversity group. Compared with the high diversity group, both the low and moderate diversity groups showed a significantly increased risk of AD (adjusted hazard ratio [aHR] 1.08; 95% CI 1.04-1.12, and aHR 1.11; 95% CI 1.09-1.13, respectively). No significant interaction was observed by infant sex or maternal history of asthma or AD. CONCLUSION: Lower dietary diversity during the first year of life was associated with an increased risk of subsequent AD in this nationwide cohort. These findings support an association between early, diverse complementary feeding and lower AD risk, warranting confirmation in prospective studies.