Infant growth and breastfeeding patterns: The Japan Environment and Children's Study.

Breastfeeding is recommended as the ideal nutrient source for infants, with the benefit of reducing future metabolic risk. Rapid catch-up growth in infancy has been associated with increased later adiposity and cardiometabolic risk. Few studies have evaluated growth and feeding patterns in Japanese infants. This study aimed to clarify growth and feeding patterns in Japanese infants. Participants were children enrolled in the Japan Environment and Children's Study cohort. Height, weight, and body mass index (BMI) at 3-4 and 8-12 mo, and 1, 1.5, 2, 2.5, and 3 yr were compared between three feeding patterns at 6 mo: breast-, formula-, and combination-feeding. The breast-, combination-, and formula-feeding groups comprised 19,987, 8,804, and 5,071 infants, respectively. In the combination-feeding group, measured indices at 3-4 mo were lower than in the breastfeeding group (p < 0.0001), although combination-fed infants showed catch-up growth from 8-12 mo to 1 yr (p < 0.05). Breastfed infants showed rapid growth and high BMI from birth to 3-4 mo, and slow growth and low BMI after 8-12 mo. Combination- and formula-fed infants showed slow growth in early infancy then rapid growth. Catch-up pattern observed in combination- and formula-fed infants warrants growth monitoring and access to individualized feeding support.