Less Is More: The Power of Single-Strain Probiotics
The importance of gut health continues to increase, as does its management. There has been an explosive growth in products which influence, alter, or support the gut microbiota. A good example of such products are probiotics, viable micro-organisms which confer health benefits to the host when administered in adequate amounts (FAO/WHO, 2002).
Because of these benefits it is no surprise the use of probiotics has rapidly increased, and with it the availability of commercial products. However, choosing the right probiotic in this abundance of products is not an easy task.
One of the major distinctions in the current probiotic market is the difference between single- and multi-strain products. The idea behind multi-strain products is mainly that by combining multiple probiotics in the same product, each strain brings its own benefits and as a result, the final product can list multiple advantages. Although this may sound logical at first, there are some important considerations to this reasoning that should not be neglected. In what follows, only spore-forming probiotics will be kept in mind: spores offer superior stability during storage, feed processing and within the animal. As such, comparing a single-strain product containing spores with a multi-strain product without spores would not be fair either way.
Inter-product competition
If multiple probiotics are used in one product, an aspect of inherent competition might be introduced, depending on the characteristics of the strains used. This is especially the case if they are part of the same genus (Bacillus for example). Due to their similarities, the strains are expected to compete for similar requirements, including nutrients and space. This could potentially diminish the intended beneficial effect, as the probiotics might challenge each other. Strains of the same genus are often also active at the same location within the gastrointestinal tract, adding to the logic that they could compete with one another.
Omnipotent products do not exist
The reasoning behind combining multiple probiotics into one product, resulting in multiple benefits for said product, leads to the question how many strains can be combined. If that number increases, the list of benefits should become much more substantial as well. As such, in theory this logic could lead to a product containing an unlimited number of strains, and thus with a very long list of benefits. Some commercial probiotic products do follow this reasoning, but as is evident from the market, they are far from dominating compared to single- or limited multi-strain products.
In vivo trials show no added benefit of multi-strain products
A recent field study evaluated three Bacillus strains (two B. subtilis and one B. amyloliquefaciens, Chr. Hansen) in supporting broilers during a Clostridium perfringens-based necrotic enteritis (NE) challenge. The trial included the three strains on their own as well as all three in the same treatment to examine the potential synergy between the strains. Despite the claimed superiority of the multi-strain combination, the data showed that the single strains were not outcompeted, regardless of whether technical performance or health parameters were evaluated. As such, from in vivo data, there seems to be reason to doubt any claimed multi-strain superiority.
Conclusion
Despite the goal of creating synergy and superiority in multi-strain probiotic products, there are multiple logical arguments to keep in mind when probiotic strains are combined. The commercial market seems to agree with this reasoning, as multi-strain probiotic products do not outcompete single-strain products. Finally, recent peer-reviewed research confirmed that multi-strain probiotics work, but do not offer any clear superiority over single-strain formulations.