Ten questions about "nutrition"

1. The accurate and relatively complete definition of the word "nutrition" should be: the process that the body ingests food, digests, absorbs and metabolizes it in the body, and uses the substances beneficial to the body in food as the process of constructing the tissues and organs of the body to meet the needs of physiological functions and physical activities.

2. In the process of life activities, human beings need to constantly ingest food from the external environment in order to obtain the nutrients needed for life activities. These nutrients are called "nutrients" in nutrition.

3. Nutrients needed by human body are: carbohydrates, lipids, protein, minerals, vitamins and **5 categories. Among them, nutrients that cannot be synthesized in the body but must be obtained from food are called "essential nutrients". There are more than 40 kinds of essential nutrients for human body, including 9 kinds of amino acids, 2 kinds of fatty acids, 7 kinds of macroelements, 8 kinds of trace elements, 14 kinds of vitamins and water.

4. Carbohydrates, lipids and protein are called "macronutrients" because of their high demand and their significant proportion in the diet; Minerals and vitamins are called "micronutrients" because they are required in relatively small amounts and account for a small proportion in the diet.

5. Nutrients have three functions in human body: one is to supply energy for life, labor and tissue cell function; Second, provide the human body with "building materials" to form and repair body tissues; Third, provide regulatory substances to regulate the physiological functions of the body. It can be seen that nutrients are the material basis and the foundation of health.

6. At the molecular level, the human body is composed of protein, lipids, carbohydrates, water and minerals. Take a man weighing 65kg as an example: water is about 40kg, accounting for more than 60% of the body weight; Lipid is about 9kg, accounting for 14% of body weight, of which 1kg is estimated to be necessary for life activities, and the rest is energy storage, which can change according to the activity state of human body. Protein is about 1 1kg, accounting for 17% of body weight. Most of protein exists in the body as a basic component, and the loss of more than 2kg will lead to serious physiological dysfunction; Carbohydrate does not exceed 200g, which mainly exists in the form of glycogen in the body and can be used for consumption and storage.

7. At the cellular level, the human body consists of cells, extracellular fluids and extracellular solids. Cells are the main components of human functions. According to tissue location, cells are usually divided into muscle cells, fat cells, epithelial cells, nerve cells and so on.

8. At the organizational level, the human body is composed of tissues, organs and systems, so that its weight is equal to the sum of adipose tissue, skeletal muscle, bone, blood and other internal organs. Adipose tissue, including fat cells, blood vessels and some supporting structures, is the main place to store fat.

9. Food ingested by the human body must be processed into small molecules in the digestive tract before it can enter the body. This process is called digestion. After food is digested, the process of small molecular substances formed by nutrients entering the blood or lymph through the digestive tract is called "absorption".

10. The main parts of food absorption are duodenum and jejunum at the upper end of small intestine. Ileum is mainly the reserve of absorption function and the compensatory part of absorption function, while large intestine mainly absorbs water and salt.

Learning registered dietitians can help us to know more about the physiological functions, digestion and absorption, deficiency and excess, nutritional evaluation, dietary reference intake and food sources of various nutrients. On this basis, learn food nutrition, special population nutrition, mass nutrition, clinical nutrition and related diseases. Finally, learning registered dietitians should understand two commonly used research methods in nutrition, namely molecular nutrition and nutritional epidemiology. Discuss with Hanhan Nutrition.