International Group of Probiotic Scientists Weighs in on Flawed Conclusions From New Scientific Papers

ISAPP cites methodological concerns and laments irresponsible media coverage

The International Scientific Association for Probiotics and Prebiotics (ISAPP) has released a critique of two recent papers (here and here), which were published last week in the scientific journal Cell.

The ISAPP Board of Directors, along with two other senior scientists, say the study authors failed to place their results into the context of what is already known about probiotics and human health. They also cited a number of methodological concerns that may have affected the results.

The primary criticism of the two studies is that they did not include any human health measures (or “clinical endpoints”)—instead, they focused exclusively on measures of the subjects’ resident microbes and on the ability of the test product to colonize the gastrointestinal tract. Many studies do not include clinical endpoints, but in their absence, no conclusions can be made about the actual or likely effectiveness of a probiotic. The ISAPP scientists emphasize that, by definition, probiotics must have a scientifically demonstrated health effect and that colonization is not required for probiotics to be effective.

Furthermore, dozens of well-conducted human studies have demonstrated that different probiotics work for different purposes. ISAPP authors cite the gold-standard evidence (for example, in Cochrane reviews) showing different probiotic strains are effective for a number of health conditions.

ISAPP also lamented the irresponsible coverage of the studies by media around the world—coverage that erroneously led readers to believe that the studies tested probiotics and found them to be ineffective. These lay press articles not only contained factual errors, but also made generalizations about all probiotics rather than the specific product tested in the two studies. Some of the misinformation was traced back to the academic journal’s press release about the article.

The full ISAPP critique of the papers and the media coverage appears here on their blog.

The ISAPP Board of Directors includes 10 respected international experts in the field of probiotics:  Prof. Seppo Salminen, PhD; Prof. Daniel Merenstein, MD; Prof. Robert Hutkins, PhD; Prof. Michael Cabana, MD MPH; Dr. Karen Scott, PhD; Prof. Colin Hill, PhD; Prof. Glenn Gibson, PhD; Prof Eamonn Quigley, MD; Prof. Gregor Reid, PhD, MBA; Prof. Sarah Lebeer, PhD; and non-voting Executive Science Officer, Dr. Mary Ellen Sanders, PhD.


ISAPP is the non-profit association of global scientists whose consensus panels have reaffirmed or established the internationally-accepted definitions of probiotics and prebiotics. The association was founded in 2000 with the mission of advancing scientific excellence in the field of probiotics and prebiotics, and since then over 60 peer-reviewed scientific papers have been authored under the auspices of ISAPP by its Board of Directors and their collaborators.