Study on the improvement effect and safety of supplementing animal bifidobacterium lactis subsp. CP-9 on the intestinal health of older infants and young children: a multi-center, double-blind, randomized, controlled trial

INTERVENTION: Group A: Experimental group:Probiotics, 6‐12 months old;Group C: Experimental group:Probiotics, for 12‐36 months, excluding 12‐month‐olds;Group D: Control group :Placebo, 12‐36 months, excluding 12‐month‐olds;Group B: Control group:Placebo, 6‐12 months; CONDITION: None PRIMARY OUTCOME: Changes in gut microbiota (16s rRNA); SECONDARY OUTCOME: Adverse reactions and concomitant medications;Blood routine;Allergy related: incidence of respiratory allergies and skin allergies;Functional gastrointestinal diseases (Rome IV, bloating, nausea, reflux, etc.);Fecal immune inde X(sIgA);Dietary Scale;Disease and infection investigation: fever, frequency of medical treatment;Frequency and duration of diarrhea occurrence;Blood immune and inflammatory markers (CRP, IL‐2, IL‐6, TNF ‐ a);Height, weight, head circumference;Frequency and duration of constipation occurrence;Fecal Form Scale (BSFS) ‐ frequency of bowel movements; INCLUSION CRITERIA: 1. 6 to 36 months old; 2. Gestational age ranging from 37 to 42 weeks; 3. Birth weight between 2500 and 4000 grams; 4. The mothers of the infants have no diagnosed metabolic diseases such as diabetes, nor any infectious diseases like hepatitis B or HIV; 5. Good compliance, able to follow the clinical trial requirements and regulations; 6. The subjects or their guardians have signed the informed consent form.