People are eager for health, but their health literacy is often not high. Many people still lack scientific health knowledge, and are often subjectively misled by sense of smell, taste and vision, so that the body can not get a balanced nutritional intake; Objectively, it is often misled by the flood of health information in society, exaggerated propaganda and spirit of unscrupulous merchants, which not only costs money, but also has negative effects and even delays the illness. The story that experts know cows tells us that only by understanding the nature of things can we know why! With the development of the times, the methods and theories of health preservation are also developing. Therefore, mastering and applying more scientific knowledge and ending the superstition of health preservation has become the common demand of people in today's times. The three senses refer to the objective demand and essence of human body for energy; That is: know the energy and nutrition needs of human body, know the value and function of external energy, and know how to balance supply and demand. First, we know that the basic substances that make up the human body structure are carbohydrates, protein, minerals and water, which constitute the basic tissue cells of the human body. In order to maintain life and health, ensure normal growth and development and engage in labor, the human body needs to get nutrition from food every day. The organic and inorganic substances in these foods that can be digested, absorbed and utilized by the human body are called nutrients. Nutrients can be divided into six categories: carbohydrates, fats, protein, inorganic salts, vitamins and water. The main functions of these nutrients in the body are to supply energy, form and repair tissues, and regulate physiological functions. Among them, heat energy, like water, is the energy that the human body must obtain to maintain life activities in order to meet the needs of the body. The human body's demand for heat energy is consistent with its consumption of heat energy, that is, energy demand = basic metabolism+physical activity+energy consumption of food special power. Heat energy mainly comes from carbohydrate, fat and protein; Everyone's energy needs will vary with gender, age, labor intensity and physical fitness. Eating well does not mean eating nutritionally, eating nutritionally does not mean balanced nutrition, and the highest state of nutrition is balanced. A healthy human body needs the participation of exercise, medical care and mentality besides food, which is the basic energy source. Second, understand the value and function of external energy 1, food 1) carbohydrates mainly come from cereals and root foods, such as various cereals and potatoes. Vegetables and fruits are the main sources of cellulose and pectin except a small amount of monosaccharides. 2) Protein eggs mainly come from meat, eggs and beans. Its main functions are: forming and repairing body tissues; Regulating physiological functions; Constitute substances with special physiological functions, such as enzymes, hormones, antibodies, etc. And supply heat energy. 3) Fat, the main sources are various vegetable oils and refined animal fats. Its main physiological functions are: providing essential fatty acids; Carrying fat-soluble vitamins; Provide deep heat energy and necessary heat energy reserves for the body; Let the rice feel full; Increase the flavor of food and protect vitamins and other substances in vegetables and other foods from oxidation due to contact with oxygen. Modern medical research has found that excessive intake of carbohydrates will be stored in the body in the form of fat; This is also an important factor for most people who don't like sports to gain weight. 4) Inorganic salts There are dozens of elements known to exist in organisms. Except for carbon, hydrogen, oxygen and nitrogen, all other elements are collectively called inorganic salts. Rich in body content, such as calcium, magnesium, potassium, sodium, phosphorus, chlorine, sulfur and so on. , called macro elements, and those that are rare or even trace in the body are called trace elements. Inorganic salts are widely distributed in food and can generally meet the needs of the body. The inorganic elements that are easy to lack are calcium, iron and iodine, especially children, teenagers, pregnant women and wet nurses. Deficiencies of calcium, iron and iodine are more common. 5) vitamins, according to solubility, vitamins can be divided into two categories; One is fat-soluble vitamins, such as vitamins A, D, E and K; The other is water-soluble vitamins, such as vitamins B2, B6, B 12, C, etc. Because it can't be synthesized in the body or the amount of synthesis is insufficient, although the required amount is very small, it must be supplied by food. Its main function is to regulate physiological functions. It is known that many vitamins participate in the synthesis of coenzyme and play an important role in substance metabolism. When a certain vitamin is deficient in diet for a long time, firstly, the reserves of vitamins in tissues are reduced, then biochemical defects and abnormal physiological functions appear, leading to histological defects, and finally various clinical symptoms appear. 6) Water is an important part of human body, accounting for 60%-70% of body weight. People should supplement enough water every day according to the different environment and labor intensity.