Probiotic tablet

What are probiotics?

In 2002, the World Health Organization defined probiotics as “live microorganisms, which, when administered in adequate amounts confer a health benefit on the host”.

Probiotics are live bacteria that are beneficial for our health, especially our digestive system. When consumed in adequate amounts, these microorganisms can provide a variety of health benefits. For example, they help maintain a balanced gut microbiota by promoting the growth of good bacteria and inhibiting harmful ones.

Probiotics can improve digestion, enhance nutrient absorption, and support a strong immune system. They are commonly found in certain foods like yogurt, kefir, as well as in dietary supplements.

What you need to know about bacteria

Bacteria are often described as “good” or “bad” but not so long ago the general belief used to be that all bacteria were bad. This is because the first bacteria we identified were those that caused illness.

Today, we know that almost all bacteria are either harmless or beneficial. In fact, several types of bacteria are essential to our survival. On the other hand, only a very small number of bacteria actually pose a pathogenic threat or are potentially harmful to humans.

Among the “good bacteria”, probiotics stand out as particularly beneficial to human health.

What is a probiotic strain?

Bacteria are classified into genus, species and strains. Each strain of bacteria has its own genetic composition, which results in different characteristics. Bacteria strains are populations of bacteria that descend from a single individual or pure culture.

In the same way that a Great Dane has different characteristics from a Chihuahua, regardless of whether they are both dog breeds, bacteria of different strains have characteristics that differentiate them from bacteria of other strains.

The importance of bacteria strain specificity

Different probiotic products contain different probiotic strains. That’s why it’s not enough to say a product contains “lactic acid bacteria” or “Limosilactobacillus reuteri”. The product must specify the species and strain name to know which probiotic the product contains. For example, Limosilactobacillus reuteri DSM 17938.

A probiotic product with Limosilactobacillus reuteri (for example, L. reuteri NCIMB 30242) is not equal to another probiotic product that contains another strain of Limosilactobacillus reuteri (for example, L. reuteri DSM 17938).

Different strains of probiotics can have different effects on the body. For example, one strain may help improve digestion while another may help to boost the immune system. Individuals can target specific health concerns more effectively by choosing probiotic strains that are known to have specific health benefits, according to their proven clinical efficacy.

Clinically proven to be effective

It’s important that a probiotic strain has been tested in clinical studies to ensure it’s safe and that the amount is adequate and effective. A product's label should indicate the strain of probiotics and all properties associated with that strain. Products developed based on clinical studies must contain the exact same strain and dose as those tested in the trials.

“Colony Forming Units” (CFU) and gut colonization

Good probiotics colonize the human gut temporarily - this is what allows a probiotic to help restore a healthy balance of good and bad bacteria in the gut.

CFU, or “Colony Forming Units” is an estimate of how many viable bacteria cells there are in a single dose, such as a tablet. This measurement indicates the potential effectiveness of the product since a higher CFU count suggests a greater concentration of viable probiotic cells.

Probiotics must be taken regularly to provide health benefits. A daily intake of probiotics, whether from food or supplements, ensures adequate and stable levels of bacteria in the GI tract.


In summary, not all bacteria are probiotics and not all probiotics are equal. Strain specificity is important since different strains of probiotics can have different effects on the body. Additionally, probiotic strains should be tested in clinical studies to ensure their safety and effectiveness.

You can learn more about probiotics and bacteria strains in our Learning Lab.
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