Probiotics are used to improve intestinal immunity, promote nutrient absorption, and produce nutrients. 1. Improve intestinal immunity: probiotics can produce some of the chemicals that kill harmful bacteria, but also compete with harmful bacteria for living space and resources, which is beneficial to intestinal health and improves intestinal resistance to disease. 2. Promote nutrient absorption: Some probiotic strains can produce specific digestive enzymes in the digestive tract to help the human body better digest the ingested food in order to better absorb the nutrients in the food. Probiotics can also competitively inhibit harmful microorganisms from absorbing nutrients from food in the human digestive tract. 3. Nutrient production: Probiotics can produce vitamins in the digestive tract, including pantothenic acid, vitamin B, vitamin K, etc. They can also produce short-chain fatty acids, antioxidants, amino acids, etc. for human absorption. All of the above medications should be used under doctor’s supervision, avoid self-medication.