What is a probiotic?

Probiotics are often thought of as ‘friendly bacteria’, however there’s a bit more to it than that. Probiotics are defined as ‘live microorganisms which when administered in adequate amounts, confer a health benefit on the host’.1,2

The probiotic concept dates back to the early 20th century, with Professor Elie Metchnikoff’s theory that there were health advantages in replacing proteolytic bacteria in the colon with saccharolytic species, preferably those producing lactic acid.

Probiotic Bacteria Blue - Text Content with Image 460x259

How to identify a probiotic

Probiotics commonly belong to the genera Lactobacillus or Bifidobacterium, although other microorganisms (including the yeast, Saccharomyces boulardii) can also be considered probiotic.


Probiotic microorganisms are classified to strain level (e.g. Lacticaseibacillus (genus) paracasei (species) Shirota (strain)), which is important because their characteristics and actions are considered to be strain-specific (see Table for an illustration of the name in comparison to a vitamin). 

Probiotic table 2

When choosing a probiotic, the following aspects should be considered:


·        The full name of the strain(s): not all probiotics are the same and the properties per bacterial strain differ.

·        Minimum count of live cells at end of shelf-life: the product formulation and dosage also play a role in the effectiveness of a probiotic. Select a product that states how many live bacteria are present at the end of the use-by date. Because the number of CFU's can decrease during the storage period, only mentioning the number of bacteria at the time of production is not enough. This information has to be supported by quality control procedures.   

·        Evidence to support its safety: lactic acid bacteria such as lactobacilli have been used for centuries and consumed in fermented foods, but not all have the GRAS (Generally Recognized As Safe) status. A producer of probiotic products must be able to demonstrate that both the bacterial strain(s) used and the end product are safe.

·        Scientific evidence for survival in the gastrointestinal tract: to be able to be called probiotics, a bacterial strain must arrive alive in the intestines after consumption. Not only the bacterial strain(s) but also the end product (dairy drink, pill, powder) must be tested.

·        Scientific evidence to confirm efficacy: check whether scientific studies (human studies) have been carried out with the product (ie not just the strain or individual strains) and what the clinical endpoints of the study were.


To check the safety and survival of Lacticaseibacillus paracasei Shirota visit the fundamental research pages.

For further guidance on what to consider when choosing a probiotics and how to decipher a product label visit:

·         https://isappscience.org/eu-probiotic-label/

·         http://internationalprobiotics.org/wp-content/uploads/IPA-guidelines-to-qualify-a-microorganism-as-probiotic-June-2-2017.pdf

Are there any probiotic health claims?

To date, the European Food Safety Authority (EFSA) has not approved an application for a probiotic health claim.  Furthermore, the European Commission believes the term ‘probiotic’ carries an implied health claim, and so the word is not permitted on packaging and marketing materials.


Despite the current regulatory restrictions, there is ongoing high-quality research into probiotics for human use.


At an International Codex level an Argentinian proposal was recently accepted for the production of a guidance document regarding probiotics. This process is ongoing and may require a few years of discussion between all UN members.




1. FAO/WHO Working Group (2002) Report on Drafting Guidelines for the Evaluation of Probiotics in Food. London, Ontario, Canada, April 30 and May 1, 2002. Available at: https://www.who.int/foodsafety/fs_management/en/probiotic_guidelines.pdf.

2. Hill et al. (2014) Nature Reviews Gastroenterology & Hepatology 11:506-514S.