Since the components of dietary fiber are very complex, and the detection method used has not been standardized so far, its precise definition has not been determined. Its rough definition is as follows.
Dietary fiber is mainly a polysaccharide that cannot be used by the human body, that is, a polysaccharide that cannot be digested by digestive enzymes in the human gastrointestinal tract and is not absorbed by the body. Such polysaccharides are mainly derived from complex carbohydrates in plant cell walls, and can also be called non-starch polysaccharides, that is, non-α-glucan polysaccharides.
In recent years, it has been suggested to call unavailable oligosaccharides or resistant oligosaccharides. Also included in the ingredients of dietary fiber.
Before 1970, there was no term "dietary fiber" in nutrition, but only "crude fiber". Crude fiber was once considered to be a non-nutritive ingredient that has no nutritional effect on the human body. Nutritionists consider that eating too much crude fiber will affect the body's absorption of nutrients in food, especially trace elements. However, through nearly 20 years of research and investigation, it has been discovered and realized that this "non-nutrient" is closely related to human health. It plays an important role in preventing certain diseases of the human body. At the same time, it also recognizes the concept of "crude fiber". It is no longer applicable, so the term crude fiber is discarded and replaced with "dietary fiber".
Dietary fiber is a carbohydrate that cannot be digested by the human body. It can be divided into two basic types when dissolved in water: soluble fiber and insoluble fiber. Cellulose, hemicellulose, and lignin are three common types of water-insoluble fibers, which are found in plant cell walls; while pectin and gum are water-soluble fibers, which are found in non-fibrous substances in nature.
Common foods such as barley, beans, carrots, citrus, flax, oats and oat bran are rich in water-soluble fiber. Water-soluble fiber can slow down digestion and excrete cholesterol most quickly, so it can increase blood sugar in the blood. And cholesterol control above the ideal level, can also help diabetic patients to reduce insulin and triglycerides. Insoluble fibers include cellulose, lignin and some semi-fibers, as well as wheat bran, corn bran, celery, peel and root vegetables from food.
3 main features
1. Water absorption. Dietary fiber  has a strong ability to absorb water or combine with water. This effect can increase the volume of feces in the intestinal tract, speed up its transportation, and reduce the time for harmful substances to contact the intestinal wall.
2. Stickiness. Some dietary fibers have strong viscosity and can form mucus-type solutions, including pectin, gum, seaweed polysaccharides, etc.
3. Combine the role of organic compounds. Dietary fiber has the effect of combining cholic acid and cholesterol. 
4. Cation exchange. Its effect is related to the carboxyl group of uronic acid, which can combine inorganic salts in the gastrointestinal tract, such as potassium, sodium, iron and other cations to form dietary fiber complex, which affects its absorption.
5. Bacterial fermentation. Dietary fiber is easily digested by bacteria in the intestinal tract, among which soluble fiber can be completely digested by bacteria, while insoluble dietary fiber is not easily digested. The short-chain fatty acids produced after glycolysis, such as ethyl, propyl, and butyl can be used as energy sources for intestinal cells and bacteria. Promote intestinal peristalsis, reduce flatulence, and improve constipation.
Dietary fiber is a carbohydrate that cannot be digested by the human body. It can be divided into two basic types when dissolved in water: soluble fiber and insoluble fiber. Cellulose, partial hemicellulose and lignin are three common types of water-insoluble fibers, which are found in plant cell walls; while pectin and gums are water-soluble fibers, which are found in non-fibrous substances in nature. Common foods such as barley, beans, carrots, citrus, flax, oats and oat bran are rich in water-soluble fiber. Water-soluble fiber can slow down the speed of digestion and excrete cholesterol most quickly, and help regulate immune system function , To promote the excretion of toxic heavy metals in the body. Therefore, the blood sugar and cholesterol can be controlled above the ideal level, and it can also help diabetic patients to improve insulin levels and triglycerides. Dietary fiber classification
Insoluble fibers include cellulose, lignin, and some hemicelluloses, as well as wheat bran, corn bran, celery, peel and root vegetables from food. Insoluble fiber can reduce the risk of intestinal cancer. It can also prevent constipation and diverticulitis by absorbing toxic substances in food, and reduce the toxins excreted by bacteria in the digestive tract. Most plants contain both water-soluble and water-insoluble fiber, so a balanced intake of water-soluble and water-insoluble fiber in the diet can achieve different benefits.
5 Health value
The cellulose in human diet is mainly contained in vegetables and rough processed grains. Although it cannot be digested and absorbed, it has the functions of promoting intestinal peristalsis and facilitating excretion of feces. Herbivores rely on symbiotic microorganisms in their digestive tract to decompose cellulose for absorption and utilization. Food cellulose includes crude fiber, semi-crude fiber and lignin. Food cellulose is a substance that cannot be digested and absorbed. It used to be considered a "waste", but now it is believed to play an important role in protecting human health and extending life. Therefore, it is called the seventh nutrient .
1. It helps the intestinal Escherichia coli synthesize multiple vitamins.
2. Cellulose has a small specific gravity and a large volume. It occupies a large space in the gastrointestinal tract, which makes a person feel full and helps lose weight.
3. The bulk of cellulose can stimulate the gastrointestinal tract after eating, increase the secretion of digestive juice and enhance gastrointestinal motility, and can prevent and treat diabetes constipation.
4. A high-fiber diet can slow down the absorption of sugar by delaying gastric emptying, changing intestinal transit time, and soluble fiber forming a gel in the intestine. It can also reduce the secretion of intestinal hormones such as gastric inhibitory peptide or glucagon, reduce the stimulation of pancreatic islet B cells, reduce insulin release and increase the sensitivity of peripheral insulin receptors, and enhance glucose metabolism.
5. In recent years, studies have proved that a high-fiber diet increases the binding of insulin receptors on monocytes in patients with type I diabetes, thereby saving the amount of insulin required. It can be seen that eating a high-fiber diet for diabetic patients can not only improve hyperglycemia, reduce the application dose of insulin and oral hypoglycemic drugs, but also help lose weight, but also prevent constipation, hemorrhoids and other diseases.
7 Current status of dietary fiber intake
According to the "Reference Intake of Dietary Nutrients for Chinese Residents" issued by the Chinese Nutrition Society in 2000, the appropriate daily intake of dietary fiber is 30.2 grams
The US Food and Drug Administration (FDA) recommended daily dietary fiber intake is 25-30 grams
The actual national situation is that the average daily intake of dietary fiber per person is only 13.3 grams
The daily intake of dietary fiber in most first-tier city residents is less than 10 grams, which is seriously insufficient
The dietary fiber intake of Chinese residents is seriously insufficient, which is an important factor in the high incidence of wealthy diseases
Although there are many vegetables containing dietary fiber, do not eat too much, otherwise the health hazards will be great:
1. A large amount of fiber supplementation may cause hypoglycemia.
2. A large amount of fiber supplement may reduce the digestion and absorption rate of protein.
3. A large amount of fiber supplement may affect the absorption of calcium, iron, zinc and other elements. Eating a large amount of dietary fiber, while delaying the absorption of sugar and lipids, also hinders the absorption of some major and trace elements, especially calcium, iron, zinc and other elements.
4. A large amount of fiber supplementation may "overwhelm" the gastrointestinal tract of diabetic patients. The gastrointestinal function of diabetic patients is weak, gastric emptying is often delayed, and even gastroparesis of varying degrees appears.
Therefore, when we supplement dietary fiber, we should also pay attention not to overcorrect. We should have a variety of foods, mainly cereals, and match the thickness.
9 Dietary fiber in vegetables
1. Dried bamboo shoots: Dried bamboo shoots contain a variety of vitamins and cellulose, which have anti-cancer and anti-cancer effects. After obese people eat bamboo shoots, it can also promote digestion, which is a good product for obese people to lose weight.
Dried bamboo shoots
2. Pepper: Pepper is rich in dietary fiber, which can clean the digestive wall and enhance digestive function, and can inhibit the production of carcinogens and accelerate the elimination of toxic substances, which can reduce blood fat and control cholesterol.
3. Pteridium aquilinum: The dietary fiber contained in it can promote gastrointestinal peristalsis, have the effects of lowering the air to relieve bowel movements, clearing the intestines and detoxification. Regular consumption can also lower blood pressure, relieve dizziness and insomnia, and treat rheumatoid arthritis. The dietary fiber contained in it can promote gastrointestinal peristalsis, have the effects of lowering the air to relieve bowel movement, clearing the intestines and detoxification. Regular consumption can also lower blood pressure, relieve dizziness and insomnia, and treat rheumatoid arthritis.
4. Cauliflower: Cauliflower is low in energy and high in dietary fiber, which is helpful for fighting many cancers.
5. Spinach: Spinach contains a lot of vitamins and dietary fiber, which can promote human metabolism, delay aging, and eliminate toxins in the body. The dietary fiber in spinach can play a good laxative effect.