In recent years, microbiota testing has become increasingly popular. Patients are often offered a stool test and then promised that it will identify which bacteria are "missing," which ones are "harmful," and which specific probiotic will help restore balance.
It sounds logical. But can a single test really answer all of these questions?
Modern science provides a more cautious answer: no.
At present, no laboratory microbiota test can automatically identify the optimal probiotic or create a personalized treatment plan based solely on the test results.
What Does a Stool Test Actually Show?
The gut microbiota is an extraordinarily complex ecosystem consisting of thousands of species of bacteria, fungi, viruses, and other microorganisms. These microbes live not only in the intestinal lumen but also on the intestinal mucosal surface, where they actively interact with the immune system.
Most modern tests analyze only a stool sample. This means the laboratory evaluates only part of the microbial ecosystem—primarily the microorganisms that have been excreted from the body. Such testing cannot fully reflect the composition of bacteria interacting with the intestinal mucosa, nor can it show how actively they perform their biological functions.
Not every sampling method allows for an objective assessment of the microbiota. At VIVERE Clinic, samples for microbiome analysis using next-generation sequencing (NGS) are collected according to a specialized protocol that helps ensure the most accurate and informative results.
In addition, results may vary depending on diet, previous infections, antibiotic use, the timing of sample collection, and even the laboratory methodology.
Why Can't We Simply Identify a "Deficiency" of Certain Bacteria?
A common assumption is that if a test shows a low abundance of a particular bacterium, it is enough to supplement it with a probiotic.
In reality, the situation is much more complex.
Most probiotics contain specific well-studied strains that are not necessarily permanent residents of the gut. Their purpose is not to "colonize" the intestine but to interact with the existing microbiota, support the intestinal barrier, influence local immune responses, and create conditions that promote the restoration of the natural microbial balance.
Therefore, a low level of a particular bacterial species in a laboratory report does not automatically mean that a probiotic containing that same microorganism should be prescribed.
Why Can't One Test Determine Treatment?
The choice of a probiotic depends on much more than the composition of the microbiota.
Healthcare professionals also consider:
- clinical symptoms;
- the confirmed diagnosis;
- previous infections;
- the use of antibiotics and other medications;
- dietary habits;
- coexisting medical conditions;
- immune system status;
- results of other laboratory and diagnostic tests.
It is the overall clinical picture that determines whether a probiotic is needed at all and, if so, which specific strain has the strongest scientific evidence for the patient's particular condition.
What Does Current Science Say?
The International Scientific Association for Probiotics and Prebiotics (ISAPP) emphasizes that probiotic effects are strain-specific. This means each strain has its own evidence base and cannot be recommended simply because a test indicates a "deficiency" of a related bacterial species.
Research has also shown that the same probiotic may behave differently in different individuals. This depends on the composition of each person's native microbiota, genetic characteristics, and local immune responses.
That is why modern medicine is gradually shifting from the principle of "treating the test results" to "treating the patient."
Are Microbiota Tests Useful Then?
Yes, but they should be used only when clinically indicated and interpreted correctly.
In research settings, microbiota analysis helps scientists better understand the relationship between the gut ecosystem, the immune system, and the development of various diseases.
In clinical practice, test results may serve as one source of information for healthcare professionals, but they should never be the sole basis for selecting a probiotic or prescribing treatment.
For this reason, personalized microbiome therapy requires a comprehensive approach that combines clinical evaluation, assessment of lifestyle, nutrition, coexisting conditions, and, when appropriate, laboratory testing.
Conclusion
A stool test cannot automatically determine which probiotic is right for you. It does not provide a complete picture of the microbiota, cannot assess its functional activity, and cannot replace a physician's clinical judgment.
Modern medicine focuses not on treating laboratory findings but on identifying the causes of symptoms and selecting evidence-based therapy for each individual clinical situation. This principle forms the foundation of personalized microbiome therapy.
References:
1. Hill C, Guarner F, Reid G, et al. The ISAPP consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014. DOI: 10.1038/nrgastro.2014.66
2. Sanders ME, Merenstein DJ, Reid G, et al. Probiotics and prebiotics in intestinal health and disease: from biology to the clinic. Nat Rev Gastroenterol Hepatol. 2019. DOI: 10.1038/s41575-019-0173-3
3. Suez J, Zmora N, Segal E, Elinav E. The pros, cons, and many unknowns of probiotics. Nat Med. 2019. DOI: 10.1038/s41591-019-0439-x
4. Zmora N, et al. Personalized Gut Mucosal Colonization Resistance to Empiric Probiotics... Cell. 2018. DOI: 10.1016/j.cell.2018.08.041
5. Integrative HMP (iHMP) Research Network Consortium. The Integrative Human Microbiome Project. Nature. 2019. DOI: 10.1038/s41586-019-1238-8
