Dr. Anna Pastorino , nutritionist biologist, talks about the benefits and the various types of fibers.
Dietary fiber is included in the category of carbohydrates, even if they do not give any energy intake . This category includes all those molecules, mainly carbohydrates (with the exception of lignin), which, given their complex chemical structure , are neither digested nor absorbed by the stomach and small intestine and, once they have reached the terminal tract of the intestine, the colon, undergo a whole or partial fermentation process by the enzymes of the intestinal flora .
Dietary fiber constituents
Fibers are naturally present only in foods of plant origin: vegetables, legumes, fresh fruit, nuts , whole grains and oil seeds and can be divided into:
- Soluble : if they tend to form a gelatinous compound inside the intestinal lumen , allowing the stomach to empty more slowly and interfering with the absorption of carbohydrates and lipids.
- Insoluble : if they retain a lot of water, they swell and increase the mass of the stool , allowing to speed up its transit in the intestinal lumen .
There are many beneficial effects of fiber, some already mentioned above:
- the best known and most appreciated is the intervention on intestinal motility and the prevention of constipation ;
- they can facilitate weight loss , facilitating the achievement of a sense of satiety , as they help to increase the volume of food ingested and to slow down the emptying of the stomach ;
- they allow to slow down the absorption of carbohydrates and fats , consequently lowering the levels of glucose and cholesterol in the blood;
- they decrease the duration of intestinal transit, thus reducing the contact times with potential harmful compounds, significantly lowering the risk of tumors;
- they have a prebiotic action , they are able to stimulate the growth of "good" bacteria present in the intestine by rebalancing the composition of the bacterial flora , this action has been particularly demonstrated by inulin.
The Italian Society of Human Nutrition (SINU) indicates a daily fiber intake of 25 g per day . Given the positive role for human health, some scientific societies and international bodies suggest even higher quantities of fiber: for cancer prevention the World Cancer Research Fund recommends at least 30 g per day , while for cardiovascular prevention the European Society of Cardiology 40- 45 g per day .
Meyer, D., & Stasse-Wolthuis, M. (2009). The bifidogenic effect of inulin and oligofructose and its consequences for gut health. European journal of clinical nutrition , 63 (11), 1277–1289. https://doi.org/10.1038/ejcn.2009.64