By definition, fibers are substances of plant origin that are neither digested nor absorbed by our digestive tract. However, our intestinal flora, by degrading them, allows us to absorb carbohydrates in a variable and partial way, hence their contribution up to 2 cal/g to our energy intake.
In addition to their effects on our transit, they would also reduce our energy intake by 5 to 10% (satiating effect of fibers), to reduce our total cholesterol level by 10 to 15% (but we need a lot of it) and to limit the increase in glycemia (blood sugar level) after a meal. By slowing down the digestion and absorption of sugar, soluble fiber helps us fight cravings. Certain minerals such as calcium or phosphorus are less well absorbed if the diet is too rich in fibre. Be careful therefore if you have mineral deficiencies (magnesium, calcium…) or if you consume a lot of refined fibers (such as bran for example) to boost your lazy transit: make sure to enrich your diet with mineral sources (pulses and green vegetables in particular) and drink enough because otherwise, instead of facilitating transit, they will form a plug. Finally, the fibers would prevent the appearance of certain cancers.
Soluble and insoluble fiber are different.
The former are called soluble because they dissolve in water. In the intestine, they swell the intestinal bolus giving it a viscous consistency which facilitates intestinal transit. They are found in oats, barley, dried fruits (prunes, dates, figs…), fresh fruits (currants, raspberries, blackberries, pears and apples with skin…), fresh vegetables (Brussels sprouts, celeriac, broccoli, chervil…) and dried (red beans, chickpeas, lentils…).
The second, called insoluble, absorb large amounts of water and increase the weight of the stools, their water content and their plasticity. They fight against the constipation, provided you drink well. They are found in wheat bran, whole grains, wholemeal bread…
How do we meet our daily fiber needs?
25 to 30 g This is the amount of fiber that an adult should consume each day according to the recommendations of the National Health Nutrition Program (PNNS), while most women and men absorb half as much daily.
Our daily fiber needs are 40% met with a 40 g bowl of All Bran cereal, 50% with 6 slices (160 g) of wholemeal bread or 400 g of cooked peas, and 25% with 2 to 3 dried prunes or 300 g broccoli or 100 g raspberries.
