The prebiotics

Requirements of a good prebiotic

Prebiotics are non-digestible organic substances, capable of selectively stimulating the growth and / or activity of one or a limited number of beneficial bacteria present in the colon.

The study of prebiotics began in the 1990s with the aim of supplying specific nutrients to the intestinal bacterial flora, stimulating their growth. After learning the beneficial properties of live lactic ferments and colliding with objective difficulties in making them survive gastric digestion, scholars sought to provide the body with optimal nutrients to stimulate the growth of beneficial microflora. These studies gave rise to prebiotics, substances which, according to the current classification, must have very specific characteristics, which can be summarized as follows:

- they must overcome, almost unharmed, the digestive processes that take place in the first part of the digestive tract (mouth, stomach and small intestine); - they must represent a fermentable nutrient substrate for the intestinal microflora, in order to selectively stimulate the growth and / or metabolism of one or some bacterial species; - they must positively modify the microbial flora in favor of the symbiotic one (bifidobacteria, lactobacilli); - they must induce positive luminal or systemic effects for human health.

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These strict constraints exclude many substances from the category of prebiotics which, although they are not absorbed or hydrolyzed in the first section of the digestive tract, are non-specific fermented by numerous bacterial species. The most known and studied prebiotics are the oligosaccharides and in particular the inulin and the fructo-oligosaccharides (FOS). Some substances also include other substances such as galactoligo-saccharides (TOS), gluco-oligo-saccharides (GOS) and soy-oligo-saccharides (SOS).

Effects of prebiotics on human health

Prebiotics perform many beneficial functions for the human body.

Decrease of fecal pH with acidification of intestinal contents

The fermentation of prebiotics by the intestinal microflora originates lactic acid and short chain carboxylic acids which, by virtue of their acidity, create favorable environmental conditions for the growth of symbionts (Bifidobacteria, Lactobacillus Acidophilus) and hostile for the development of pathogenic microorganisms. Consequently, we witness a decrease in the "enemy" flora and its toxic metabolites which, when present in excessive concentrations, favor inflammation of the mucosa and alter its permeability, with negative repercussions on the health of the entire organism. Among them we remember ammonia (toxic for the brain), biogenic amines (highly toxic), nitrosamines (hepato-carcinogens) and secondary bile acids (powerful promoters of colon cancer).

To the short chain fatty acids produced by the fermentation of prebiotics are also attributed protective functions against inflammatory bowel diseases. Butyric acid appears to have a preventive effect on the development of colon cancer; moreover the FOS improve the bioavailability of the isoflavones present in legumes (substances to which are ascribed protective effects towards different types of cancer, such as breast and prostate cancer).

Mucosal tropism and cell proliferation

The short chain fatty acids (especially butyric), besides reducing the proliferation of pathogens and having antiputrefactive properties, are an excellent nourishment for the cells of the mucous membrane of the colon and contribute to improve trophism and efficacy. All this translates into a better absorption of nutrients at the expense of toxic ones.

Increased bioavailability of minerals

The prebiotics indirectly facilitate the absorption of water and some minerals in ionized form, in particular calcium and magnesium.

Cholesterol-lowering action

In some studies prebiotics have proved useful in reducing the plasma concentration of cholesterol and, to a lesser extent, of triglycerides. Probably, as often happens when we talk about cholesterol, the effectiveness of these substances depends on the type of diet of the subject: the more it is rich in saturated fats and cholesterol and the greater the effects of prebiotics.

In nature oligosaccharides are present in numerous edible plants such as chicory, artichoke, onion, leeks, garlic, asparagus, wheat, bananas, oats and soy. At the industrial level, inulin is obtained mainly from chicory root (an industrial waste is transformed into a precious product). Starting from this fiber, other prebiotics, such as FOS, can then be produced by enzymatic hydrolysis. In the industrial field, fructo-oligosaccharides are also obtained from sucrose, according to a process known as transfructosylation.

Intake doses and possible side effects

The recommended intake doses of the two best known and studied prebiotics (FOS and inulin) generally range from 2 to 10 grams per day. Only if taken at high doses can cause mild gastrointestinal disorders such as flatulence, meteorism and diarrhea; to avoid these disorders, it is advisable to gradually increase the intake dose, until reaching the regimen dose within a few weeks.

The prebiotic dietary supplements are particularly suitable for those who follow a diet low in fruit and vegetables, must recover from an antibiotic therapy or suffer from gastrointestinal disorders (in this case it is good to talk about it first with your own doctor as, depending on the case, prebiotics may have opposite effects to those hoped for).