BACKGROUND Emerging evidence suggests that diet plays a significant role in the development of inflammatory bowel diseases. This study aimed to assess the association between early-life food diversity and the incidence of inflammatory bowel diseases from a nationwide retrospective cohort study in South Korea.

METHODS This study incorporated 1 242 295 South Korean infants who participated in the National Health Insurance Service. Food diversity was categorized as "high" or "low" based on vegetables, fruits, grains, meats, fish, and eggs consumed during weaning. The association between food diversity and inflammatory bowel disease incidence was examined and subgroup analysis was conducted according to food diversity groups. The Cox proportional hazards model was used to estimate the risk of inflammatory bowel disease, with hazard ratios adjusted for demographic factors. Propensity score matching was employed for evaluating the general characteristics of the study population.

RESULTS Among the infants evaluated, 71.3% of those who developed ulcerative colitis and 66.0% of those who developed Crohn's disease did not consume high-diversity food. Individually, food diversity, solid food intake frequency, antibiotic usage, and breastfeeding status were not significantly associated with inflammatory bowel disease incidence. However, the combination of high food diversity and frequent solid food intake (≥3 times/day) was associated with a lower risk of ulcerative colitis by 48% (adjusted hazard ratio: 0.52, CI 0.28-0.98, P = .0426).

CONCLUSIONS Food diversity, combined with the frequency of solid food intake, during infancy is associated with the incidence of ulcerative colitis. Promoting a diverse diet during infancy may be important in preventing the development of IBD.