Longitudinal trends and determinants of dietary supplement administration during the first two years of life: a Korean birth cohort

Objectives Dietary supplement administration has steadily increased in Korea, but evidence on administration of dietary supplements to infants remains limited. This study investigated the longitudinal trends and determinants of supplement administration in infants from birth to 24 months of age. Methods A longitudinal birth cohort study enrolled 137 infants born at ≥28 weeks of gestation, and followed them at 2, 6, 12, and 24 months. Structured questionnaires assessed supplement administration, feeding methods, family history of allergic diseases, and demographics. Feeding was categorized as breastfeeding, formula feeding, or mixed feeding. Atopic dermatitis and food allergy were diagnosed using standardized criteria. Results Overall, 82% of infants were given supplements during the study period. Probiotics and vitamin D were the most frequently administered at all ages, while multivitamin administration increased markedly after 12–24 months (38.6%). Supplement administration differed by feeding method: breastfed (29.4%) and mixed-fed (5.0%) infants had a higher percentage of iron supplementation at 12 months compared with formula-fed (0%). Multivitamin administration was more common among infants without a family history of allergies (low-risk group: 32.6%) compared with those with a family history of allergies (high-risk group: 23.4%). Infants born via cesarean section were significantly more likely to be given dietary supplements at 2–6 months (OR = 8.09, 95% CI: 1.79–36.49), 6–12 months (OR = 14.88, 95% CI: 1.91–116.10), and 12–24 months (OR = 5.16, 95% CI: 1.09–24.35). Conclusions This study found a high percentage of supplement administration among Korean infants, with frequent administration of probiotics and vitamin D from early infancy. Over time, supplement types became more diverse, with usage trends varying by feeding method and allergy risk. Cesarean-born infants were more likely to be given supplements. These findings provide descriptive data on how supplements are administered to Korean infants and suggest a basis for exploring the implications of early-life supplement administration.