In the early years, people thought that dietary fiber had neither nutritional effects nor could be digested and absorbed by people, so they did not pay much attention to dietary fiber, but focused more on nutrients such as protein, fatty acids, and vitamins. However, as the incidence of obesity, cardiovascular diseases, diabetes, and cancer in the West became higher and higher, while the incidence of these diseases in some regions of Africa was lower, people found that high-fat and high-protein diets often led to a high incidence of these chronic diseases, while diets based on plant foods were more conducive to the prevention of these chronic diseases by studying the relationship between their diets and diseases, and thus researchers began to take a great interest in dietary fiber. This has led researchers to take a keen interest in dietary fiber. Dietary fiber is indispensable for a healthy diet. Dietary fiber is mainly divided into insoluble fiber (such as lignin, cellulose, certain hemicelluloses, etc.) and soluble fiber (including pectin, gum and mucilage, etc.). Dietary fiber can absorb water, increase the volume of feces and promote defecation; dietary fiber can “scrub” the intestinal wall of people’s colon and rectum, accelerate the digestive system to the transport of food intake, reducing the retention time of harmful substances in the body. Nowadays, people often sit in the office, less and less activity, when the diet lacks sufficient dietary fiber, people may become constipated, long-term constipation is a high risk of colon and rectal cancer. Nowadays, it has been a consensus that dietary fiber-rich cereals and vegetables and fruits have anti-cancer effects, which are also supported by a large number of experimental results and epidemiological studies. The 2nd edition of the guidelines “Food, Nutrition, Physical Activity and Cancer Prevention” published by the World Cancer Research Fund and other global authorities states that foods containing dietary fiber can prevent colon and rectal cancer, etc.; there is also some evidence that foods containing dietary fiber can prevent esophageal cancer. In addition, dietary fiber has an indirect protective effect. This is reflected in the low energy of dietary fiber itself, which can prevent obesity, etc., as well as prevent the occurrence and development of some tumors caused by overnutrition. Researchers have collected data on stool weight from 20 populations in 12 countries and studied the risk of colorectal cancer in relation to dietary fiber (non-starch polysaccharides), stool habit, stool weight and stool passage time in different populations. It was found that the average daily stool weight was negatively correlated with the risk of colorectal cancer and positively correlated with the intake of dietary fiber, and that the amount of fecal excretion increased with the increase of dietary fiber. So where is dietary fiber mainly found? Animal foods, such as chicken, duck, fish, meat, milk and eggs, which are highly recommended by many people, do not contain dietary fiber. Dietary fiber mainly exists in whole grains, coarse grains and grains, vegetables and fruits, and plant foods such as beans, such as brown rice, sweet potatoes, millet, oats, buckwheat, etc. It is appropriate for each person to consume about 25 grams per day.