"Reduce your garlic intake." "Eat more garlic." "Avoid dill." Such contradictory recommendations appear in the results of intestinal microbiota tests conducted by private companies, often sold at a high price.

The microbiota sparks curiosity. Comprising around 50 trillion bacteria, viruses and other microorganisms, it interacts with the immune, neurological and digestive systems, among others. Its imbalance is linked to certain conditions such as diabetes, obesity, cancer, autoimmune and inflammatory diseases, as well as neuropsychiatric disorders like depression.

Riding the wave of abundant research avenues and public enthusiasm, many "specialized" companies offer microbiota tests to assess its composition, without medical prescriptions. They sometimes come with recommendations or therapeutic advice.

Are they reliable? To clarify, researchers from the Pharmabiotic Research Institute (PRI), based in France, sent the same stool sample to six companies – five European and one American, including two medical laboratories. The cost ranged from €150 to €300. Upon receipt, these results were discussed by a panel of 21 experts from eight countries, who gathered for an online workshop.

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