Dietary fibers are compounds that originate mainly from carbohydrates. They belong to the so-called non-starch polysaccharides. According to some literature, these compounds are also classified as nondigestible proteins.
The best definition is that dietary fibers compose a diverse group of organic molecules, usually of plant origin, that are not subject to hydrolysis in the human digestive tract.
The most important and best-known compounds in this food group are as follows:
- Plant resins
- Beta glucans
Cellulose is the main component of the cell membranes of many plants; it is a huge molecule that is indigestible by the human body. It belongs to the group of insoluble dietary fibers and has no large capacity to bind water. Cellulose is the main ingredient in wheat, bread and wheat bran. The main sources of cellulose are integral and black flour, bran, cabbage, beans, cucumber skins and peppers.
Hemicellulose consists of a group of molecules and differs from cellulose in that it is partially digested by the human body. The main sources of hemicellulose are cooked sauerkraut, peas, soybeans and cereal grains.
Pectins are mainly contained in fruit (particularly unripe fruit). They are a soluble dietary fiber. Major sources of pectin are apples, strawberries, blackberries, raspberries, carrots and potatoes.
Lignin is often involved in the construction of the plant cell wall, but it is not present in food in large quantities. The main sources of lignin are strawberries, pears, green beans, eggplant and cereals. Ripe vegetables and fruits have more lignin than do unripe vegetables and fruits.
You should eat dietary fibers every day. The recommendation is to eat at least 30 grams of fibers in the form of fruit (about two servings of fruit a day). They are very important because they regulate digestion and may help people who want to lose weight.
To help you select and plan an appropriate intake of dietary fiber, we have created a table showing how rich in these compounds certain foods are.
|Food||Quantity of dietary fiber (grams) in 1 cup|
Note: These values apply only to raw foods. The thermal or mechanical processing of food (e.g., peeling fruits) can reduce the amount of dietary fiber in that food.
How can dietary fiber help you lose weight?
These compounds have a high capacity for water absorption (water binding) whereby they increase their own capacity and swell. In this way they increase the volume of stool and accelerate intestinal motility, which leads to better digestion.
In addition, the increase in volume and swelling means prolonged retention of food in the stomach, which increases feelings of fullness, thereby allowing you to easily handle an energy-reduced diet. They do not contain many calories, so they are very often (and justifiably) part of the menu for many diets.
They also reduce the utilization of fat, as they absorb (bind) and remove it from the body, preventing its use as an energy source. It is therefore a good idea to eat fruits before eating a meal, because you will eat dietary fiber that will bind the fat that entered your stomach during the meal and throw it out of the body, thus reducing your caloric intake. These compounds do not affect the utilization of vitamins and minerals - only fat. This fact is very important for those who want to lose weight, because by eating an adequate amount of fruit before meals, you can achieve a phenomenal effect. The prerequisite for realizing this effect is a sufficient intake of liquids. It is best to take one serving of fruit and two glasses of water before meals.
Insoluble dietary fibers have a much lower capacity for binding water than do soluble dietary fibers. Therefore, they swell less and do not create a feeling of fullness as soluble dietary fibers do.
Because of this, nutritional guides recommend taking in more soluble dietary fiber (contained mostly in fruits and vegetables) and less insoluble dietary fiber (contained mostly in wheat and wheat products).