Fiber: what they are and what they offer us

Fiber or dietary fiber is defined as polysaccharides that are not affected by the digestive enzymes of the small intestine, but only certain bacteria can break them down. For this reason they pass through the digestive system and provide negligible or zero amounts of energy to the body. From raw and raw plant foods, dietary fiber is consumed mainly in the form of parts of the plant wall or even as whole cells. The most common polysaccharides that belong to the category of fiber are cellulose, hemicellulose, pectins, β-glucans, gums and mucus. Dietary fiber yields approximately 2 Kcal / g at least for those cases where the diet provides small and moderate amounts of fiber.

Foods rich in dietary fiber are almost all raw or unprocessed foods of plant origin. Usually, fruits and vegetables that have peel, fiber or spores in their composition are good sources of fiber. In addition, whole grains and legumes are rich sources of fiber. A basic distinction of fiber is made based on their solubility in water. Thus, they are distinguished in insoluble such as lignins, cellulose and hemicelluloses and soluble such as pectins, β-glucans, mucus and gums.

Dietary fiber serves some important physiological functions. The role of dietary fiber in the proper functioning and health of the digestive system is particularly studied. Consumption of sufficient amounts of dietary fiber is considered crucial for the proper functioning of the intestine. Epidemiological studies have shown that diets rich in dietary fiber have a protective effect against the occurrence of colon cancer as well as diversions. They also lead to an increased volume of stool and pass very quickly into the large intestine, thus effectively helping with the problem of constipation. They cause satiety and thus facilitate the weight loss process, because they help the dieter to follow the diet program without feeling strongly the feeling of hunger.

It is often said that we should not eat legumes or spinach with cheese, because the fiber contained in these foods reduces the absorption of certain minerals, especially calcium and iron, thus contributing to the occurrence of nutritional deficiencies. Fiber itself does not affect the absorption of minerals, but phytic acid, a compound found in many plant foods and usually linked to their fiber, binds metals such as zinc (Zn), iron (Fe) and calcium. (Ca) and reduces their bioavailability. Particularly vulnerable to the negative effects of high dietary fiber consumption are considered people who have very limited consumption of animal products and meat, especially if they are people who have a limited dietary intake (such as the elderly) or particularly high nutrient requirements (such as are the children).

In addition, soluble fiber helps reduce postprandial insulin secretion and better regulate blood sugar (glucose). For this reason, we recommend that diabetic patients eat plenty of leafy vegetables and fruits with their skins, as well as whole grain foods. Reducing bad LDL cholesterol, which is primarily responsible for causing atherosclerosis in the blood vessels, as well as reducing bile secretion, are some of the benefits of including fiber in our diet.

Recommendations for dietary fiber intake converge to 10-13 g of fiber per 1000Kcal, an amount that for most corresponds to 20-35 g of dietary fiber per day. Unfortunately, this perspective often causes us to become overwhelmed when it's time to start a new diet. Most of them are herbal, non-addictive, can be used for long-term use and by special groups of the population, such as pregnant women, children, diabetics and vegetarians. However, they should be consumed with plenty of water and avoided by people who suffer from an obstruction or intestinal atony, are taking anticoagulants or have undergone obesity surgery.

 Kontopidou Irini

Clinical Dietitian, M.Sc.

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