What’s all the fuss about probiotics?

Probiotic food and nutritional additives have gained a lot of attention in both research and mainstream media lately. There has been a huge growth in interest in probiotic products over the last 10 years around the world. There is a growing body of evidence to support their importance in our diet; both to treat and prevent specific diseases and as part of a healthy diet. Perhaps unsurprisingly, the global demand for, and production of probiotic products has risen tremendously; to an estimated 32.6 billion US$ in 2014, with a predicted annual increase of 20%. The European market accounts for 42% of this, and dairy products account for 70%. Despite this, the European Union nutritional and health claims regulation adopted in December, 2012 barred the labeling of products as pro-biotic, claiming they are “unauthorized health claims”. This ruling, and these EU regulations have been criticized by many, we believe rightly so, as being overly strict and placing too high a burden of evidence on health claims for which there is in fact a great deal of high-quality scientific support. Before we get into the potential benefits of probiotics and what evidence there is to support those benefits we thought we would take a moment to provide a little bit of background information regarding our digestive system, the human “microbiome”, the term “probiotic” itself, and the history of fermentation and probiotics. This topic is a pretty big can of worms, so while we will do our best to distill the important information, we have to break this post up into a number of sections.


Probiotic products’ are products that contain ‘probiotics’. Definitions of probiotics vary; the word is derived from pro and biota, meaning “for life”. A good definition for the purpose of this blog post is:

Probiotics are live bacteria and yeasts that when consumed confer health benefits on humans.


Acidophulus bacteria in filmjolk consist of different strains, just like the species domesticated dog can does. Many of the positive health effects of probiotics are strain-specific, which is one of the reasons these effects are so complicated to describe.

Bacteria and yeasts (as well as viruses and other single-celled microbes) are naturally found on and in every body. These microbes, which make up the human “microbiome” are so numerous and important that they have even been called our “hidden organ”. Most of these microbes live in our gastro-intestinal tract or “gut” (stomach, large intestines, small intestines colon), but we also have rich microbial communities on our skin and in our mouths, and, for women, in our vaginas; we’ll be focusing on our gut microbes in this post. An estimated 100 trillion microorganisms representing more than 500 different species inhabit every normal, healthy digestive system. In fact, if you count up all these cells, the ones that are in the human body but are not “human” cells, there are 10 times more not human cells in a human body than there are human cells. These microbial communities are very complex and they change in relation to many factors, including if we have taken antibiotics or even if we have a carbohydrate-rich or protein-rich diet, if we are vegetarian or not; in fact, our gut communities change in relation to our diet in as little as 24 hours1. In addition to responding to what food we put into our bodies, the microbes in our gut do A LOT for use. They break down and digest our food into nutrients that we can absorb into our bodies. They also produce important nutrients (vitamins, amino-acids, etc…) that we may not consume in our food. They regulate our immune system and they protect against disease-causing pathogens we may consume orally. These are a few of the many things our gut microbes do for us, and in the proceeding sections of this multi-part blog post on probiotics, as well as in future posts, we’ll go into them in a bit more detail.

The most common types of probiotics are in the bacterial groups (genera) Lactobacillus and Bifidobacterium, but many more exist, and even yeasts (which are fungi) are getting increased attention lately for their potential to confer benefits upon us. One of the tricky things with probiotics is that many positive effects of probiotics are strain-specific, meaning specific bacteria- and yeast-strains do specific things. A “strain” refers to a specific group within a species ex. a golden retriever and a cockerspaniel are two strains of the species domestic dog. As we’ll describe later, this strain specificity of probiotic properties has made research into the health benefits of probiotics and labelling of probiotic microbes much more difficult. In kombucha, the most numerous bacteria are Komagataeibacter sp. (formerly called Gluconacetobacter) and ‘Lactobacillus’, and Acetobacter sp. The most common yeasts are Pichia sp. and Saccharomyces sp 2.

So, if every healthy body contains trillions of helpful microbes anyway, the question is why it is beneficial to consume additional products containing probiotics? One reason to consume probiotic products is to replenish the good bacteria in your guts after e.g. an antibiotic treatment. This has been one of the most common “medical” uses of probiotics; doctors routinely advise patients to eat some live yogurt after a round of antibiotics to help recolonize the GI tract after the antibiotics have potentially killed a lot of the microbes living there. Another reason is to treat a number of diseases that affect us, including chronic diseases like Crohn’s disease, ulcerative colitis, Irritable Bowel syndrome, eczema or viral or bacterial diarrhea. Recent research has also indicated, however, wider ranging potential health benefits of probiotic supplementation including reduced inflammatory responses, reduced allergies, lower blood pressure, weight management, and even cancer prevention. However, the evidence to support these claims is complex and while it is very convincing for some of the aforementioned claims (like treating diarrhea) it is less certain or very preliminary for others. In the following posts on probiotics we’ll go into more detail about the evidence supporting the health benefits of probiotic supplementation, and the consumption of probiotic fermented foods and drinks like kombucha, as well as recent changes in the food labelling laws that affect how probiotic products can be marketed. But first, in the the next post we’ll discuss how to get probiotics and what are good sources of them.



1: Clemente JC, Ursell LK, Parfrey LW, Knight R. 2012. The Impact of the Gut Microbiota on Human Health: An Integrative View. Cell 148: 1258-1266.


2: Marsh AJ, O’Sullivana O, Hill C, Rossa RP, Paul D. Cottera PD. 2014. Sequence-based analysis of the bacterial and fungal compositions of multiple kombucha (tea fungus) samples. Food Microbiology 38: 171-178.

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