What are Probiotics?

To know the answer to the question “what are probiotics?”, we need to go back to the second half of the 20th century.

From the first definition in 1965, the concept of Probiotics has changed over the years until its latest definition in 2001, when a panel of experts under the auspices of WHO and FAO defined Probiotics as “living microorganisms that when consumed in appropriate amounts confer healthful effects on the host”(1). This definition is still accepted by the scientific community today.

(1)Report of the FAO/WHO Expert Consultation on the Evaluation of the Health and Nutritional Properties of Probiotics in Foods, including Milk Powders containing Live Lactic Acid Bacteria 2001

Probiotics and Prebiotics

The term “Probiotic” means “pro-life” and with it we refer to all those microorganisms that exercise a beneficial function in our organism.

We should not confuse Probiotic (microorganisms) with Prebiotic (carbohydrates used by microorganisms)

We should not confuse it with “Prebiótico” since in the latter case we are referring to carbohydrates or dietary fiber that will be used by the microorganisms to feed themselves from it. In other words, prebiotics act as a substrate for probiotics, something like their “gasoline”.

Origin of Probiotics

The origins of probiotics go back more than a century, when scientist and Nobel Prize winner Elie Metchnikoff (1845-1916) discovered that populations consuming one type of fermented milk had a longer lifespan than the rest of the population.

Elie Metchnikoff
Elie Metchnikoff

Later, a French pediatrician, Henry Tissier, observed Y-shaped bacteria (i.e., bifid form) in infant stool. He also observed that the amount of these bacteria present in the body was lower in those children who had episodes of diarrhea. Tissier was able to isolate this bifid-form bacteria, a Bifidobacterium.

On the other hand, in 1917, the German scientist Alfred Nissle managed to isolate a non-pathogenic strain of Escherichia Coli from the faeces of a German soldier who, being in an area with a high prevalence of shigellosis, he, unlike his colleagues, did not have any symptoms of diarrhoea.

Most common microorganisms in probiotics

The most common bacterial species in today’s probiotics are

  • Species of the genus Lactobacillus (e.g. L. casei)
  • Species of the genus Bifidobacterium
  • Although to a lesser extent, the Saccharomyces boulardii yeast is also used as well as bacteria of the species E. coli and others of the genus Bacillus.
  • Streptococcus and Enterococcus species

Benefits of probiotics

The benefits of probiotics can be non-specific, species-specific or even strain-specific.

Among these benefits that probiotics bring to the body:

  • They generate a resistance to the colonization of pathogenic bacteria through a process of competitive exclusion.
  • They acidify the environment to create a hostile environment that prevents the growth of pathogenic species.
  • Produce bacteriocins that inhibit the growth of pathogens
  • They favour the production of short chain fatty acids, (acetate, propionate and butyrate) that favour the integrity of the intestinal membrane and give it energy.
  • It favours the regeneration of the intestinal epithelium.
  • Regulation of the gastrointestinal transit.
  • They contribute to the immunological training by increasing the secretion of immunoglobulin A (IgA) and modulating the level of cytokines.
  • They promote antigenic tolerance to food antigens.