”The human body must constantly take in food from the outside world, digest, absorb and metabolize it through the digestive tract, and use the nutrients in food to maintain the whole process of life activities. This process must ensure that the body is provided with substances that produce enough energy to build and repair tissues and organs. There are more than 50 types of nutrients required by the human body, which can be summarized into 7 categories: proteins, carbohydrates, lipids, minerals, trace elements, vitamins, dietary fiber and water. The main functions of these nutrients are: 1) to provide energy; 2) to serve as materials for building and repairing tissues and organs; 3) to play a regulatory role in the metabolism of substances in the body. No single food can provide all the nutrients people need, therefore, we must have a diversified diet and reasonable nutrition, so that the intake of various nutrients and the body’s need for these nutrients to achieve a balance, so that the body’s internal environment is stable, people can have health and less disease. Lack of certain nutrients can cause nutritional deficiency diseases, such as: calcium deficiency causes rickets, iron deficiency causes anemia, etc.. Excessive intake of certain nutrients can cause obesity, hypertension, diabetes and cardiovascular disease and other affluent diseases, and long-term disorders of the internal environment can even lead to the occurrence of tumors. Therefore, it is recommended that we should start from the perspective of disease prevention, eat reasonably and avoid diseases from the mouth (not only infectious diseases), and believe that we will definitely eat for health and longevity as long as we take each meal seriously.