The term dietary fiber it was coined in 1953, but the health effects of foods with a high fiber content were known since ancient times; already in 430 BC Hippocrates described the laxative effects of whole wheat compared to refined wheat.
Dietary fibers are the main components of the cell wall of plants and, due to their complexity, they are not degraded or decomposed by enzymes present in the first part of the intestine. All those molecules, mainly carbohydrates (with the exception of lignin), belong to this category. ), which due to their complex chemical structure are neither digested nor absorbed by the stomach and small intestine and, once they arrive in the terminal tract of the intestine, the colon, undergo a whole or partial fermentation process by the enzymes of the intestinal flora.
Based on their metabolism and digestibility, fiber can be divided into soluble And insoluble. Among the soluble fibers there are pectins, gums and mucilages, among the insoluble ones there are cellulose, hemicellulose and lignin.
The foods richest in fiber are those belonging to the plant kingdom, such as cereals, especially whole grains, vegetables, fruit, legumes and dried fruit. Their fiber content also varies according to the cooking and ripening of the fruit or plant.
From a nutritional point of view, fibers do not provide energy to the body, but have beneficial effects on health by acting together with vitamins, minerals, polyphenols and carotenoids.
Thanks to their ability to help preserve and improve the state of health and reduce the risk of the appearance of certain diseases, fiber is now considered an excellent supplement to add to foods to increase its natural content (for example, biscuits, cereals, sweets , etc.).
The beneficial actions of fibers are mainly due to their chemical characteristics which make them able to retain water and form aggregates which increase the density of gastric juices.
The fibers also have:
- prebiotic action, in other words they are able to stimulate the growth of "good" bacteria present in the intestine by rebalancing the composition of the bacterial flora that is naturally present in it
- satiating power, as they slow down the passage of food inside the digestive tract
- ability to slow down the absorption of carbohydrates and fats, as a result, lower blood glucose and cholesterol levels
- ability to promote the elimination of unabsorbed food, improving bowel function and reducing associated disorders such as constipation (constipation) and diverticulosis
By virtue of the ability of fibers to bind mineral salts it has been shown that they can favor the absorption of some of them, such as calcium, magnesium and iron.
Regular consumption of adequate amounts of fiber is associated with a decreased risk of chronic degenerative diseases such as type 2 diabetes, cardiovascular disease and some cancers, particularly colorectal cancers, in part due to easier elimination of any carcinogenic substances and the reduction of their contact time with the intestinal mucosa.
Some soluble fibers such as pectin, thanks to the particular property of forming a gel in contact with water, are used in the food and beverage industry, for example in the preparation of jams. In addition to its importance in the food industry, pectin has also found use in medicine, for example in the administration of nasal, ocular and oral medications and in wound healing.
The amount of fiber recommended by the Italian Society of Human Nutrition (SINU) varies according to age:
- adults, at least 25 grams per day, even in the case of energy supplies of less than 2000 kilocalories per day
- childhood, 8.4 grams for every 1000 kilocalories consumed
Contraindications and drug interactions
A diet rich in fiber was generally associated with a reduced absorption of minerals in the gastrointestinal tract, since it was believed that fibers, by virtue of their ability to bind and trap minerals, could somehow limit or delay their " absorption, however, recent studies seem to demonstrate, but other studies are needed to confirm it, that fibers, through their beneficial action on bacterial flora, can play an important role in promoting the absorption of minerals.
The use of fiber-based supplements, in addition to being unnecessary if you follow a balanced diet, is strongly discouraged if you are taking drugs as some types of fiber inhibit or limit its absorption. If, on the other hand, the treating doctor decides that it is necessary to take fiber-based supplements, it is advisable to consume them with an adequate amount of water, because otherwise unwanted effects (side effects) such as swelling, abdominal tension, cramps, diarrhea, etc. could occur.Bibliography
Tan WSK, Chia PFW, Ponnalagu S, Karnik K, Henry CJ. The role of soluble corn fiber on glycemic and insulin response. Nutrients. 2020; 12:961-971
Slavin J. Fiber and prebiotics: mechanisms and health benefits. Nutrients. 2013; 5:1417-1435
Lattimer JM, Haub MD. Effects of dietary fiber and its components on methabolic health. Nutrients. 2010; 2:1266-1289
Whisner CM, Castillo LF. Prebiotics, bone and mineral metabolism. Calcified Tissue International. 2018; 102:443–479
Capuano E. The behavior of dietary fiber in the gastrointestinal tract determines its physiological effect. Critical Reviews in Food Science and Nutrition. 2017; 57:3543-3564
Italian Society of Human Nutrition (SINU). LARN 2014. Carbohydrates and dietary fiber