Fiber or dietary fiber is a plant component characterized by β-type chemical bonds and is NOT digestible for the human being; however, although not considered a real nutrient, fiber is undoubtedly a very important food component for the correct functioning of the organism, in particular of the intestine.
Soluble and insoluble fiber
Fiber is divided into soluble and insoluble, and performs numerous functions; between these:
- It confers the sense of satiety
- Regulates intestinal peristalsis and promotes the systematic evacuation of faeces
- Removes waste from the intestine
- Modulates / slows the absorption of fats and sugars
- Limits the absorption of cholesterol
- It reduces the glycemic and insulin surge
- Partially nourishes the intestinal bacterial flora
What is that
A low-fiber diet decreases fecal volume and hinders the physiological (nervous) process of triggering peristaltic contractions of segmentation and advancement.
On the other hand, despite the collective tendency to eat LITTLE fiber compared to the recommendations (which suggest about 30g / day), in some "pathological" cases it is necessary to drastically limit it to reduce unwanted symptoms or disturbances; this diet is defined low-fiber diet or low-residue diet.
For whom it is indicated
The function of the low-fiber or low-residue diet is to reduce the laxative effect on the digestive tract; the cases in which it may be necessary to apply it are mainly:
- Irritable bowel syndrome
- Colitis (inflammatory, infectious, chemical, etc.)
- Intolerances and allergies
- Pharmacological therapies
- Radioactive therapy
- Intestinal resection (for cancer, Crohn's disease, or ulcerative colitis)
- Preparations for endoscopic investigations of the itestinal tract (e.g. colonoscopy)
Logically, when normal physical conditions are restored (if possible), the low residue diet should be interrupted by replenishing the recommended amount of dietary fiber.
What to eat
In practical terms, the low-fiber or low-residue diet is a nutritional scheme poor in fruit, vegetables, cereals and legumes which, if present, MUST be processed / refined in order to at least eliminate the typical outer coating (peel, pericarp or other fibrous integuments, etc.) notoriously rich in this element (in essence, however, whole grains should be avoided).
Although not correlated with the intake of dietary fiber, even milk and dairy products (or foods that contain them) can be limited / interrupted in the administration of the low residue diet; this choice is not accidental and is based on the concept that, in most intestinal sufferings, the lactase enzymes present on the mucosa are drastically reduced, causing bacterial fermentation of lactose and the consequent accompanying symptoms (see lactose food intolerance).
To properly manage the low residue diet it is advisable:
- Look carefully at food labels
- Make sure that each food portion does not provide more than 1g of total fiber.
See an Example of a Low Residue Diet »
Cooking methods for the low-fiber or low-residue diet are moderate and non-violent; they should never excessively trigger the Maillard reaction and / or the production of toxic / irritating molecules for the intestinal mucosa (acrylamide, acrolein, polycyclic aromatic hydrocarbons, etc.). Recommended: boiling, steaming, microwave cooking and pressure cooking; in the eventualities, even slow stewing. Grilling, frying, roasting and baking at very high temperatures without a lid are NOT RECOMMENDED. Another useful tip is to avoid or not overdo the spices, such as pepper, chilli, curry, coriander, cumin, etc.
- In the event that the low-residue diet causes an excessively "stringent" effect on the stool, it is advisable first of all to increase the water supply (compromise for the elimination of fruit and vegetables) and, only later, to reinsert the fiber little by little.
- The low-fiber or low-residue diet leads to a secondary reduction in a good portion of mineral salts (magnesium, potassium, etc.), vitamin C, B-carotene and vitamin K; it is therefore advisable to evaluate together with the doctor the possibility of using a good food supplement to maintain sufficient nutritional supplies of these nutrients.