Dietary fibres are carbohydrates that our body is unable to digest, and therefore to absorb, because we do not have the right enzymes for the job. For this reason, dietary fibres are also called “non-available carbohydrates” or “non-glycemic carbohydrates”: since they are not absorbed, their consumption does not change the blood sugar level, that is, the concentration of glucose in the blood.
Dietary fibres can be divided into two broad categories: insoluble or non-fermentable and soluble or fermentable.
Soluble fibres can be fermented by the bacterial flora that lives in our intestines. Bacteria use soluble fibre as a food, and they get the energy they need to survive from this. From the fermentation, gas is produced, and for this reason, if we eat foods that contain a lot of soluble fibre, we can experience a sensation of abdominal bloating, and the same from foods containing certain short chain fatty acids. Some of these are considered very important: some research has shown that butyric acid reduces the risk of neoplastic transformation of the cells of the mucous membrane of the colon, while propionic acid seems able to reduce cholesterol synthesis. One of the great advantages that comes from consuming fermentable (or soluble) fibre is that, being very viscous, it slows down the emptying of the stomach, and therefore makes us feel full for longer. Furthermore, at an intestinal level it may slightly reduce the absorption of nutrients for some of the “less desirable” ones such as glucose or cholesterol. This is why a diet rich in soluble fibre is recommended for those with high glucose or blood cholesterol.
Insoluble fibre, on the other hand, is not fermented and, remaining intact in the intestine, increases the volume of feces and helps regulate intestinal function, helping us to faster eliminate substances that could harm us.
It is very important to consume the right amount of fibre every day, which is at least 30 g per day for a 2000 kcal diet.
Only plant-based foods contain fibre, to varying degrees depending on the product. This is one of the reasons why fruits and vegetables should be consumed at least 5 times a day. As for fruit, remember that the greatest concentration of fibre is found in the peel, which therefore should not be removed if possible. of the diet. Excellent sources of fibre are legumes, unfortunately not very commonly found on our tables, and cereals, as long as they are wholegrain. In order to consume the right amount of fibre, wholegrain foods are very important: we must learn to use them as replacements at least once a day for foods (pasta, bread, baked goods) prepared with refined flours.
And remember that correct consumption of fibre must be achieved through food, and therefore the correct diet, and not using supplements.
Department of Agricultural and Food Sciences
University of Bologna