There is a saying among people who can't mend skin that "anything can be mended". This sentence sounds simple, but it is widely circulated and has great influence. From ancient times to the present, at least China people believe it. However, to understand the meaning of this proverb, it is necessary to make it clear in two layers.

On the first floor, "what to eat". "What to eat" is the choice of food, but this choice is not only to satisfy appetite, but also to meet the needs of "hygiene", that is, how to enhance vitality, get rid of diseases and prolong life. China people have a basic view on "eating" from a long time ago, that is, everything that can be eaten is medicine, and ordinary fruits, vegetables, grains and animals have the function of nourishing the body if eaten. So at the beginning of the evolution of civilization, food and medicine were not separated. Later generations had medicine, which divided food and medicine into two categories, but the medicinal function of food was still widely valued. To a certain extent, the dietotherapy school of China health-preserving family spends a lot of time on the choice of food, that is, "what to eat". In the Song Dynasty, the food side rose, so health experts publicized its importance and necessity: