Probiotics are products (foods or supplements) containing live organisms: bacteria (known as Lactobacilli and Bifidobacteria ) or yeasts ( Saccharomyces boulardii ).
However, it is not enough for a product to contain bacteria to be a probiotic. In fact, it must be "alive" but also "active", that is, able to reach the large intestine while resisting gastric acidity in order to exert its effects on the microbes present.

The set of microbes (bacteria, viruses, fungi) that we host in our intestine is called the intestinal "microbiota".
The intestinal microbiota is a real invisible organ, made up of 100,000 billion of bacteria (10 times more numerous than our own cells!), which perform numerous beneficial metabolic functions for us.

The intestinal microbiota plays an essential role in major vital gastrointestinal functions:

- digestion of food (fermentation of carbohydrates, assimilation of gluten and lactose) - absorption of nutrients (such as calcium)
- synthesis of vitamins
- production of gas

- defense against pathogens
- maintaining the integrity of the intestinal barrier

To date, however, it is well known that the relationships between the intestinal microbiota and the human organism are not limited to the gastrointestinal system, but also concern other systems and apparatuses.
We know that there is a close connection between the central nervous system (our brain) and the intestine, so much so that the microbiota can influence our mood and intervene - for example - in the pathogenesis of depression (we speak of "intestinal brain" or "intestine-brain axis") .

One of the most important interactions, however, is the one that occurs between the intestinal microbiota and the immune system. In fact, the transmission of bacteria from mother to child during childbirth and breastfeeding seem to play a role in the formation and maturation of the immune system. A healthy and well-developed microbiota allows you to "train" immune cells to defend the body from threats and instead tolerate harmless microbes and molecules. On the contrary, an alteration of the microbiota ("dysbiosis"), involves an increased risk of allergies, infections and autoimmune diseases.

The composition of the microbiota varies with age and is influenced by a number of factors:

- excessive hygiene - stress
- cigarette smoking - infections - drugs

-diet
-alcoholic
sedentary life

These factors can alter the intestinal barrier, increasing its permeability to food, toxins and bacteria and stimulating an immune response with intestinal inflammation. Through this same mechanism, an abnormal reaction against food components ("antigens") can be established in predisposed subjects, triggering an allergy.

It is therefore important to keep the microbiota as healthy as possible. Mainly, this can be achieved through an adequate diet (mainly vegetable diet rich in cereals and fruit and vegetables at the expense of refined sugars, meat) and a healthy lifestyle. Foods rich in probiotics are fermented (yogurt, kefir, miso, tempeh), fermented drinks (kombucha), mother yeast and some fermented cheeses. Furthermore, foods represent the main source of “prebiotics”, ie substances that favor the growth of probiotics and therefore of good bacteria.

Often, especially if intestinal dysbiosis and inflammation last for a long time, supplementation with probiotic supplements may be useful and necessary.
Probiotics are defined by the "World Health Organization" as "" Live organisms which, when administered in adequate quantities, confer a benefit to the health of the host ". These are non-pathogenic bacteria that multiply in the intestine and exert a balancing action on the microflora through direct colonization. Here they help protect the intestinal mucosa, producing useful molecules and promoting colon motility. A probiotic therefore performs beneficial functions for our microbiota, increasing its component of eubiotic, ie "good" bacteria.

Initially, probiotics were mainly used on the gastrointestinal level. Here a probiotic can be extremely useful to reduce swelling and flatulence (for example in functional disorders such as irritable bowel syndrome), to prevent diarrhea during antibiotic drug treatments and - in general - for intestinal well-being.

Over the years it has been seen that they are however able to play much wider roles in immunomodulation. Probiotics are in fact able to influence the immune responses in the course of skin and allergic diseases and it is on this that the current prospects for use are focusing.

Dr. Rossana Cannas