In the last years, more and more people are becoming aware of the key role gut microbiota plays in global health and are interested in knowing more about how these bacteria can influence their risk of allergies, obesity, or even cancer.

In this sense, labs all over the world have started selling stool sample testing kits, you can do at home: you take a sample and send it back to the lab that will analyze it and detect, in theory, from celiac disease and food allergies, to leaky gut. “The right test for your health problems”, the companies selling the tests claim.

But, are these tests really useful? We asked three experts: Andrea Hardy, a registered dietitian from Calgary (Canada); Fernando Azpiroz, a gastroenterologist at Hospital Universitari Vall d’Hebron in Barcelona (Spain); and Joël Doré, Research Director at the French National Research Institute for Agriculture, Food and the Environment, INRAE- about stool and gut microbiota testing, to know more about it and its limits.


Fecal microbiota testing become more and more trendy, citizens are sometimes encouraged to do it for fun by friends or in a more serious way by some healthcare professionals. What people can learn from those tests?

Andrea Hardy: Stool testing is definitely very exciting. However, at this point, there is still a lot of research that needs to be done before we can uncover the clinical significance of performing the tests and providing health recommendations around them. I’m very excited to see how the research progresses, but at this point it’s not a good use of citizens’ money to use a fecal microbiota test to inform their health care.

Fernando Azpiroz: Simply, they are a tall tale. There is no data supporting the utility of these tests you can find over the counter. Even the complete DNA analysis still do not have a practical application, because it is something really complex. It is not just about identifying a harmful pathogen; gut microbiota is an ecosystem where we don’t know what the variations, changes or microbiota combinations that there can be mean.


For which purpose would you say this test is recommendable today?

Joël Doré: Microbiome profiles produced today are useless for the medical arena, that can only rely on standardized analysis such as the blood tests commonly prescribed. We can, nonetheless, be optimistic that in the near future clinicians will prescribe and use microbiome profiles. Scientific evidence is accumulating that makes us anticipate a relevance in many domains such as diagnostic, predictions, prevention and care, especially for chronic diseases. The proof of its benefit will nevertheless have to be established, and it may take years of application before it is eventually reimbursed.

Andrea Hardy: We need more research to support its use, specifically to show that using the markers in the test results and implementing nutrition & lifestyle recommendations based on those test results, have measurable impacts on health outcomes.


Today, as a scientist and as a dietitian, what recommendations would you make to those who have an interest in doing one of these tests?

Joël Doré: If I collect a stool sample and send it to a service company for analysis, I will in return obtain a report telling me about the composition of my intestinal microbiota. This is fun indeed. Having some numbers and odd names describing my ‘interior’ may help anyone understand that we are ‘microbial’.

As a scientist, I provided many stool samples for the development of the techniques used today. I will say it’s fun to get a selfie of “your inner self”! But if your interest is motivated by gut symptoms or a disease condition, it is a little too early to put too much hope in these tests, and I will recommend seeing a doctor.

Andrea Hardy: Save the money and focus on getting back to the basics! With any test the key question is ‘will this test inform my intervention?’. The reality is, we don’t have any research to support that. The test doesn’t inform my intervention as a dietitian, my goal with all patients interested in gut health is to increase fibre and variety, and decrease intake of animal products, alcohol, and saturated fats. The recommendations at this point wouldn’t change based on the gut microbiota testing.