Dietary fiber is a substance widely found in fruits, vegetables, cereals, beans and other aquatic plants. This article mainly summarizes the definition and classification of dietary fiber, food sources and main characteristics; analyzes the influence of dietary fiber on the absorption of various nutrients in the human body; and discusses the role of dietary fiber in disease prevention. Although the intake of dietary fiber is closely related to human health, it is also necessary to pay attention to scientific and reasonable intake of dietary fiber.

In recent years, the people's diet structure has undergone major changes. Fibrous foods decrease and fatty foods increase. High-fat and high-protein foods have become the main part of people's food consumption, which leads to diseases such as diabetes, cardiovascular and cerebrovascular diseases, and obesity, such as overnutrition and malnutrition. As the seventh nutrient, dietary fiber has outstanding health care functions.

Overview of dietary fiber

The definition of dietary fiber. There are two definitions of dietary fiber. One is to define dietary fiber as the remnants of undigested plant cells in the digestive system of mammals from a physiological perspective, including cellulose dietary fiber, hemicellulose, pectin, gum, resistant starch and Lignin; Second, from a chemical point of view, dietary fiber is defined as non-starch polysaccharides and lignin of plants, which cannot be digested and absorbed by the human body, but have one or more health benefits.

According to different water solubility, dietary fiber is divided into soluble dietary fiber (SDF) and insoluble dietary fiber (IDF). The main function of soluble dietary fiber is to reduce blood cholesterol levels and regulate blood sugar levels, thereby reducing the risk of heart disease and improving diabetes. It is mainly derived from fruits, vegetables, soybeans and oats, including pectin and other hydrocolloid substances and part of hemicellulose. The main function of non-soluble dietary fiber is to swell, which can regulate intestinal function, prevent constipation, and keep the large intestine healthy. It includes cellulose, lignin and some hemicellulose.

Food sources of dietary fiber. Dietary fiber is a plant component, mainly derived from plant foods. For example, the bran and bran of cereals contain a large amount of cellulose, hemicellulose and lignin; citrus, apple, pomegranate, kiwi and other fruits and cabbage, beets, peas, broad beans and other vegetables contain more pectin. Cereal foods, especially whole grains, are the main source of dietary fiber.

The main characteristics of dietary fiber. (1) Water absorption. (2) Stickiness. (3) Combine the role of organic compounds. (4) Cation exchange. (5) Bacterial fermentation.

The effect of dietary fiber on human nutrient absorption

Dietary fiber is an important non-nutrient, which itself cannot be directly absorbed and utilized by the body, but it has certain effects on the function of the gastrointestinal tract and the absorption of various nutrients, and is closely related to human health.

Dietary fiber and energy. As a kind of undigested carbohydrate, the content of dietary fiber in food can affect the energy density of the food ingested. Foods with higher dietary fiber have lower energy density correspondingly, so that the consumption of equal volume of food Energy is reduced.

Dietary fiber and protein. Dietary fiber has little effect on protein metabolism and nitrogen balance. High-fiber intake may change the digestion, absorption and utilization patterns of protein foods.

Dietary fiber and carbohydrates. The effect of dietary fiber on carbohydrates is mainly reflected in the effect on blood sugar. Studies have shown that water-soluble dietary fiber can delay the absorption and metabolism of carbohydrates, thereby reducing postprandial blood sugar and serum insulin rise.

Dietary fiber and lipids. Studies have shown that dietary fiber has the effect of lowering blood lipids and cholesterol, and can prevent the occurrence of coronary heart disease, obesity and cholelithiasis.

Dietary fiber and vitamins. Studies have shown that dietary fiber can reduce the bioavailability of carotene; it may reduce the absorption of vitamin B6; the fermentability of fiber may affect the absorption of vitamin B12; different fibers have different effects on the absorption of vitamin E; dietary fiber By inhibiting bile secretion, the absorption of fat-soluble vitamins will be reduced, but the absorption of non-fat-soluble vitamins will not be reduced.

The role of dietary fiber in disease prevention

Dietary fiber and cardiovascular disease. Studies have found that dietary fiber, especially soluble dietary fiber, has the effect of reducing blood lipids and cholesterol.

Dietary fiber and diabetes. Studies have shown that dietary fiber helps to delay and reduce blood glucose after meals, increase serum insulin levels, maintain the balance and stability of blood glucose after meals, and avoid drastic fluctuations in blood glucose levels.

Dietary fiber and obesity. Studies have found that suitable dietary fiber has the effect of weight control and weight loss.

Scientific and reasonable dietary fiber intake

Dietary fiber has an inseparable relationship with human health, but it is not the better. Excessive intake of dietary fiber may cause hypoglycemia, reduce the digestion and absorption rate of protein, affect the absorption of calcium, iron, zinc and other elements, and cause insufficient intake of fat-soluble vitamins. Especially for adolescents and children at the growth and development stage, too much dietary fiber is likely to take some nutrients necessary for the human body out of the body, causing malnutrition. Therefore, eat high-fiber foods in moderation, especially for children. Adults should consume 25 to 35 grams of dietary fiber daily.