“What’s in a name? That which we call a rose by any other name would smell as sweet”. These are the words uttered by Juliet to her beloved Romeo in Shakespeare’s famous play, the thrust of this famous quote being that the surnames of two rival families could not be an obstacle to love. However, in certain circumstances a name can make all the difference.
Of the various areas of recent scientific, medical and business interest, few have sparked as much buzz and controversy as probiotics. Each article published on the subject gives a different definition of probiotic, lambasts the commonly-accepted definition, or suggests a new shade of meaning. Things took an even more dramatic turn in 2006 when EFSA (the European Food Safety Authority) restricted the use of the word “probiotic” on product labels . Why are probiotics such a hot topic? What exactly is the trouble with the definition? If we want an answer to these questions, we will have to take a step back in time.
Our journey will take us to Paris at the start of the twentieth century. Here we are in one of the laboratories of the Institut Pasteur, a centre of excellence for microbiological, medical and immunological research. A stern-looking man with a dark bushy beard is staring hard down into the eyepiece of a microscope. He is a Russian biologist named Elie Metchnikoff who only a few years before had made a groundbreaking discovery in Sicily about the role of white blood cells. He won a Nobel prize for this research in 1908.
While he was studying ageing and the role of the intestine in human health, Metchnikoff theorised for the very first time that certain microorganisms could help to fight disease and improve well-being in human beings. The theory was formulated on the basis of the longevity of some Bulgarian population groups and, after a period of observation, it was conjectured that their greater life expectancy might be linked to their diet. Metchnikoff’s attention was particularly drawn by a drink made from fermented milk, a kind of yoghurt that these people habitually consumed.
The microorganisms responsible for fermentation had been isolated and identified a few years before and given the name of Lactobacillus bulgaricusin honour of the Bulgarian populations who consumed them (in 1984 they were reclassified as L. delbrueckii, a subspecies of bulgaricus).
Metchnikoff’s idea that microorganisms could affect human health by colonising the intestine and exerting a protective action not only on the intestine but on the entire body had a huge impact at the time (his discovery even caused yoghurt to be industrially produced for the first time!). But as time went by, it was labelled as just a medical practice, until scientific evidence began to emerge in the mid ‘90s which caused the idea to resurface and become one of the major themes for sciences in the field of health and nutrition.
Nowadays, probiotics are not only subjected to the intense scrutiny of medical researchers, they also drive an industry which is worth billions of euros worldwide .
As the role of probiotics for the betterment of human health became clearer, people felt a growing need to find a single and unambiguous definition for this foodstuff. Indeed, whenever science wants to gain a better understanding of something, it finds a definition for it. In 2001 the FAO and the WHO, two agencies of the United Nations dealing with food-and-health-related issues of global importance, finally provided an official definition for probiotics. Probiotics were defined as “live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance”.
This definition is actually an umbrella term for a number of different products which can be used in different ways (food, dietary supplements or over-the-counter pharmaceuticals)  and leaves a lot of questions unanswered: what is meant by the fact that the microorganisms are “living”? What difference is there between probiotics and cultures? Just how much of it “should” one consume? What is it meant by “beneficially affects the host”? Well, one question at a time.
In order to be classified as probiotics, micro-organisms must not only be alive at the time of consumption, but they must also be able to survive being inside the stomach and endure the harsh conditions caused by the aggressive acids and enzymes in the digestive system. This is exactly what sets probiotics apart from ordinary “cultures”: cultures are not expected to make it through the stomach, whereas this is a fundamental requirement for probiotics (also known as “live cultures” for this exact reason); their very reason for being is to colonise the intestinal mucous membrane, acting upon it and providing health benefits.
Studying intestinal colonisation by probiotics is no mean feat. You need to find your way through a dense jungle of minute microorganisms, all of which are extremely similar to one another. The advancement of genetics has been helpful because it allows us to identify the various strains present in biopsies and collected samples and to carry out research on specific genes which not only vary from species to species, but also from one bacterial strain to another. Clearly, though, collecting and analysing samples is quite difficult and calls for considerable outlay.
Now let’s talk about quantities: according to available scientific data, the minimum quantity required for temporary colonisation of the intestine by a microbial strain amounts to at least one billion live cells per day. Small amounts can only be taken into consideration if it has been demonstrated that the microorganism in question is able to colonise the intestine at smaller doses as well. The quantity of live cells must be specified on the label by strain and must be guaranteed up until the use-by date . It will have become clear by now that there are very strict rules which heavily limit the actions of probiotic manufacturers.
Now, here’s the crux of the matter: the benefits brought by probiotics to human health. How can they be defined? How can they be quantified? In its Guidelines on probiotics and prebiotics the Italian Ministry of Health states that, based on European Regulation no. 1924/2006, the mere fact that a probiotic colonises the intestine is not sufficient to claim that it is beneficial to health. Basically, that means it is all well and good that your bacteria has reached the intestine safe and sound, but why would that necessarily mean that it has a positive impact on your health?
Often you can find on labels something along these lines of “the product helps to rebalance intestinal flora”. But in 2006 EFSA made it known that these health claims were not acceptable. You can imagine the reaction of those who produce and sell probiotics! Italy, which is one of the biggest consumers of probiotics in the world after the USA and China, decided to authorise a looser description of what probiotics can do: “they promote a rebalancing of intestinal flora” .
Yet, there is an increasing number of worldwide studies on the effectiveness and usefulness of probiotics for the prevention and the treatment of certain ailments. So, there may indeed be health benefits, but we still need to carry out scientific studies to bear this theory out. Not only are such studies extremely time-consuming and costly, but research activities must be meticulously planned if the outcome is to be of any actual use. What is more, in some countries, research is hindered by red tape and bureaucrats who will only allow testing to be done on products that are officially registered as pharmaceuticals.
So, what do we know about the hundreds of studies carried out on probiotics over recent years? What role do these tiny little creatures play in preventing or treating diseases? Do they only have an effect on the intestine? We will be addressing this fascinating topic in our next article. Don’t miss it!
 Probiotics: definition, scope and mechanisms of action, Gregor Reid, Best Practice & Research Clinical Gastroenterology Volume 30, Issue 1, February 2016, Pages 17-25 https://pubmed.ncbi.nlm.nih.gov/27048893/ Consulted on 11/03/2021.
 Philip A. Mackowiak, “Recycling Metchnikoff: probiotics, the intestinal microbiome and the quest for long life”, Front. Public Health, 13 November 2013, https://www.frontiersin.org/articles/10.3389/fpubh.2013.00052/full Consulted on 11/03/2021.
 Schlundt, Jorgen. “Health and Nutritional Properties of Probiotics in Food including Powder Milk with Live Lactic Acid Bacteria”. Report of a Joint FAO/WHO Expert Consultation on Evaluation of Health and Nutritional Properties of Probiotics in Food Including Powder Milk with Live Lactic Acid Bacteria. FAO/WHO. Archived from the original on October 22, 2012. https://web.archive.org/web/20121022161702/http://www.who.int/foodsafety/publications/fs_management/en/probiotics.pdf Consulted on 11/03/2021.
 The Italian Ministry of Health, Single commission for nutrition and dietetics. GUIDELINES ON PROBIOTICS AND PREBIOTICS, reviewed version March 2018 http://www.salute.gov.it/imgs/C_17_pubblicazioni_1016_allegato.pdf Consulted on 11/03/2021.