Interaction of serum resistin and smoking behavior in predicting depression risk: a sex-sensitive analysis.

Infant stool frequency is strongly influenced by feeding method; breastfed infants generally defecate more frequently than formula‐fed infants. However, considerable variability exists even among breastfed infants, with defecation frequencies ranging from as many as seven times per day to as few as once every 7 days (Moretti et al., ; Steurbauta et al., ). This wide range reflects the diverse nature of normal intestinal function in healthy infants. During the first year of life, both stool frequency and consistency undergo substantial changes, which can create considerable uncertainty for parents. Concerns about infant stool frequency and associated symptoms are among the most common reasons for pediatric consultations (Gatzinsky et al., ). Despite their prevalence, infant defecation disorders are often inadequately managed, potentially leading to the development of functional gastrointestinal disorders (FGIDs). The Rome IV diagnostic criteria for FGIDs—an evolution of the Rome III criteria—define these conditions as disorders of brain–gut interaction characterized by (1) dysregulated gastrointestinal motility patterns, (2) visceral hypersensitivity, (3) altered mucosal immune function, (4) gut microbial dysbiosis, and (5) impaired central nervous system regulation of gut function (Geng et al., ). These disorders are highly prevalent in infants and young children, with an estimated global prevalence of 30% (Meng et al., ). According to the Rome IV criteria, the prevalence of FGIDs in Chinese infants and young children is approximately 27.3%, with functional constipation being the most commonly reported issue (Huang et al., ). While previous research has explored various factors influencing infant gut health, including feeding methods, gut microbiota, and genetic predispositions, the specific role of breast milk proteins in regulating defecation frequency remains poorly understood. Breast milk contains numerous bioactive proteins that can influence intestinal function. However, their contribution to infant stool frequency and their potential role in the pathogenesis of FGIDs remain unclear. Notably, human milk oligosaccharides (HMOs) and gut microbiota are central determinants of infant gut health. As key bioactive components in the early‐life gut ecosystem, they collectively modulate the intestinal microenvironment, promote immune maturation, and defend against pathogenic colonization. Their synergistic interaction supports gastrointestinal homeostasis, and accumulating evidence links this crosstalk to a reduced incidence of early‐life diarrhea. Therefore, it is essential to integrate breast milk proteins into the HMO‐microbiota‐gut axis framework to fully elucidate their coordinated contributions to infant gut health.