The role of bifidobacteria in infants is as follows:1. Maintaining the balance of normal intestinal flora, inhibiting the growth of pathogenic bacteria, preventing constipation, diarrhea and gastrointestinal disorders, etc.2. Improving the sugar tolerance of dairy products and increasing the digestibility.3. Enhancing the immune function of human body and preventing the side effects of antibiotics.4. Synthesizing vitamins and amino acids in the intestinal tract and enhancing the absorption of calcium ions in the body.5. Anti-tumor, the bifidobacteria are distributed in the stomach and intestines. The number decreases with age, infant bifidobacteria accounted for 60% of the total intestinal bacteria, and only 7.9% of the elderly over 60 years old.