First of all, we have to introduce the main actors of our researches: the probiotic bacteria. The discovery of the microbiota is revolutionizing our vision of the status of health and disease.
To define what a probiotic is, it is necessary to quote the most correct definition, given by the Food and Agriculture Organization (FAO) and the World Health Organization (WHO) in 2013: “…live microorganisms which when administered in adequate amounts confer a health benefit on the host1“…but unfortunately this is not enough to clarify the issue. Their name, “probiotics”, however, gives us an important indication; in fact, it means that they are “good for life”. They are living entities, albeit invisible to the naked eye. But you know “what is essential is invisible to the eyes2“.
What they actually do?
They are commensal bacteria and perform many beneficial activities in our intestine. They colonize our gut promoting its physiological balance, called eubiosis. In addition, they produce useful substances, such as certain vitamins, bacteriocines, and other essential compounds, maintain the balance of different microbial species by counteracting the growth of potentially dangerous species that could cause diseases, and boost immune defenses.
It’s a matter of numbers.
There are so many of them in the gut, about 100 trillion microorganisms including bacteria, and this results in a very close coexistence. The colon is highly populated and enumerates about 1011-1012 bacterial cells per milliliter3. Sometimes, however, probiotic supplementation is necessary to reestablish a healthy condition, which can be compromised by different factors, including antibiotic therapies, stress, unbalanced diet, and various diseases.
The probiotics most frequently used as food supplements are Lactobacilli and Bifidobacteria, well characterized and studied, at a daily dose of at least 1 billion to exert a beneficial effect on our bodies. It’s therefore fundamental to take care of our intestinal microbiota that supports us every day.
1Hill C, Guarner F, Reid G, et al. Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11(8):506-514. doi:10.1038/nrgastro.2014.66
2The Little Prince – Antoine de Saint-Exupéry, 1943
3Ley R.E., Turnbaugh P.J., Klein S., Gordon J.I. Microbial ecology: Human gut microbes associated with obesity. Nature. 2006;444:1022–1023. doi: 10.1038/4441022a