The excess of fibers is reflected on the organism with a set of symptoms concerning above all the gastro intestinal apparatus. It is a condition frequently related to too many fiber supplements or, more rarely, to an unbalanced diet because it is excessively rich in fibrous residues (bran, whole grains, legumes, vegetables and fruit) and is probably poor in water.
Do too many fibers hurt?
Fiber supplements (viscous and non-viscous), if taken in the context of a diet already sufficiently rich in fibrous residues, can cause an excess of fiber and the onset of some side effects. The most common fiber supplements are based on isolated fibers, namely:
- Β'-glucans: easily fermentable viscous fibers contained in barley and oats, and produced by fungi, yeasts, bacteria and algae; the most common ones in the form of supplements derive from oats, fungi and yeasts.
- Pectins: viscous fibers extracted from the peel of citrus fruits or from the pulp of the apple; they are also a gelling food additive.
- Inulin and oligofruttosi: they are extracted from chicory or synthesized starting from sucrose; they are a fairly widespread food additive. They are highly fermentable and possess a prebiotic function on bifidobacteria .
- Guar gum: viscous and soluble fibers that constitute a laxative product, but are also contained within "ready cereals" and other food products.
- Psyllium: diets low in saturated fat and cholesterol, which include 7g / day of soluble psyllium fiber, can reduce the risk of heart disease.
- Chitosan: is a non-digestible glucosamine, or a polymer of chitin; reduces fat absorption and is available as a supplement for weight loss (unproven) and for lowering cholesterol.
All these fiber supplements must be taken with plenty of water (250ml) and in the doses recommended on the label; too many fiber supplements and / or insufficient water intake in the diet (<2 liters) can contribute to the appearance of: abdominal bloating and tension, abdominal cramps, excess gas and diarrhea.
Gut side effects
There are fiber supplements that, more than others, determine the onset of specific symptoms associated with excess dietary fiber: guar gum, inulin and oligofructose, fructooligosaccharides, polydextrose, resistant starch and psyllium. In particular, the excessive intake of Guar gum and / or psyllium, coexisting with the lack of water, can determine intestinal obstruction and the worsening of symptoms in subjects with intestinal motility already in itself compromised. Furthermore, in people with colorectal polyposis, the psyllium supplement seems to be directly related to the increase in the size of precancerous adenomas.
Side effects for allergies
It is also appropriate to specify that certain fiber supplements, although NOT in excess, require special attention due to their allergenic potential. Chitin and chitosan, for example, which are extracted from the carapace of crustaceans, can cause even very serious allergic reactions in hypersensitive individuals; the same applies to the inulin extracted from chicory and to the psyllium contained in "ready cereals".
Side effects on drug absorption
Also remember that some fiber supplements may have negative drug interactions with certain drug molecules; again it is the case of psyllium, whose intake compromises the absorption of lithium, carbamazepine (Tegretol), digoxin (Lanoxin), and warfarin (Coumadin); in addition, Guar gum slows the absorption of digoxin, acetaminophen (Tylenol) and bumetanide (Bumex), and decreases the absorption of metformin (Glucophage), penicillin, and some glyburide formulations (Glynase). Pectin, on the other hand, reduces the absorption of lovastatin (Mevacor) and probably also that of clindamycin, tetracycline and digoxin.
As a precautionary measure, it is customary to recommend a distance of at least three hours between the intake of a fiber supplement and that of any drug.
Conclusions
Reach the recommended levels avoiding the side effects of excess fiber for too many supplements
The LARN (Recommended Daily Intake Levels of Nutrients for the Italian Population) recommend reaching a fiber intake of around 30g / day; in parallel , the Food and Nutrition Board of the Institute of Medicine (2004) recommends respecting a coefficient equal to 14g of fiber every 1000kcal taken, in order to lower the risk of developing cardiovascular diseases. The same institute, for adults over 50 years old, suggests maintaining a contribution of 38g / day for men and 21g / day for women.
These inputs are easily reachable with the diet but, if necessary, it is possible to use fiber supplements after consulting a food professional, who - through the food history - can estimate the right daily dose from take without incurring the side effects mentioned above.
