2.1. Study Design
This study was designed as a single-center, randomized, triple-blind placebo-controlled trial and was conducted at Xuchang Maternal and Child Health Hospital, Henan Province, China, from January 2020 to April 2021. Healthy infants born by C-section were recruited at the age of 6–24 months and divided into two age groups: 6–12 months and 13–24 months. After consent was obtained from their legal guardians, infants and toddlers were randomly assigned to either the experimental group (Lp N1115 group) or the placebo-control group, and a total of four main visits were conducted with an intervention duration of 12 weeks (During the 12 weeks of the intervention, participants consumed a packet of Lp N1115 bacterial powder (2 × 10