Abstract
Background: The complementary food introduction and consumption guidelines for atopic dermatitis and food allergy prevention have evolved; however, their impact on infant feeding practices remains unclear. This study aimed to analyze complementary food diversity trends in infants, identify vulnerable infants with limited food diversity, and examine the trends in infants with or without vulnerable factors over time. Methods: This study analyzed infants aged 9-12 months who participated in the food diversity survey, conducted as part of the National Health Screening Program in Korea from 2009 to 2020. The complementary food items included grains, vegetables, fruits, eggs, fish, and meats. Infants consuming "six" and "less than six" complementary food items were categorized into high- and low-food-diversity groups, respectively. The study employed logistic regression models to examine the trends in food diversity and vulnerable factors with an assessment of the interaction effects. Results: This study included 3,425,301 participants (51.5% male) aged 11.3 months (standard deviation, 0.8). The high-food-diversity prevalence significantly increased over time, from 30.8% in 2009 to 52.9% in 2020 (p < 0.001). Vulnerable infants included those with preterm birth, low birth weight, non-breastfeeding status, high socioeconomic status, non-Seoul residence at birth, any perinatal conditions, hospitalization due to wheezing, atopic dermatitis and food allergies. The high-diversity proportion increased significantly over the study period across all vulnerable factors (p for interaction < 0.001). However, no significant interactions were observed between the study years and vulnerable factors, except for food allergy (β Coefficient, -0.0117, p for interaction = 0.004). Conclusions: The increasing trends in high-complementary-food-diversity proportions highlight the substantial progress over the study period. However, persistent disparities in vulnerable populations underline the importance of targeted interventions, including tailored nutritional education and policies, that promote equitable dietary practices during early life.