Expert publication recommends considering dietary factors in probiotics and prebiotics research

When studying the health effects of probiotics and prebiotics, researchers often observe significant variation in responses to these gut-targeting interventions, both between individuals and between study cohorts. However, the impacts of variables that account for personalized responses to a probiotic or prebiotic substance are not known.

A new Perspective paper by an international group of eight experts, published recently in Nature Microbiology, highlights the critical role of diet in shaping the efficacy of prebiotics and probiotics. The authors examine current evidence and find that, while diet is a major determinant of gut microbiome composition and function, it has rarely been incorporated as a variable in research on the efficacy of probiotics and prebiotics. 

The experts explain that the current research on food components and the gut microbiome clearly shows how an individual’s diet, especially carbohydrates that are not completely digested in the upper digestive tract such as dietary fibers, affects the availability of substrates for microbial metabolism. These factors shape the gut microbial ecosystem, potentially affecting the success of prebiotic and probiotic interventions. The paper resulted from a workshop convened by the International Scientific Association for Probiotics and Prebiotics (ISAPP) in 2022.

The paper noted that the small number of probiotic and prebiotic trials to date that have included dietary data show intriguing results, suggesting that the area is promising for further study. For example, in one recent probiotic trial in individuals with metabolic syndrome, dietary characteristics were a key factor that differentiated responders and non-responders. In another study, participants with higher fiber intake in their background diet had a greater microbiota response and felt fuller while taking a prebiotic supplement than those with lower fiber intake. 

“Although more studies evaluating the influence diet has in responses to probiotic and prebiotic intake are clearly needed, the totality of evidence from research investigating diet and the gut microbiome strongly indicates that background diet is a major determinant of probiotic and prebiotic efficacy.”, says Prof. Maria Marco, who co-led the paper with Prof. Kevin Whelan from King’s College London.

Prof. Marco adds, “It was rather shocking to find that diet has been overlooked as a variable for predicting and understanding responses to probiotics and prebiotics. These dietary amendments are affected by diet’s impacts on the intestinal environment in the case of probiotics, and are substrates for diet-modulatory microorganisms in the case of prebiotics.”

Prof. Whelan says, “It is no longer enough to measure the host microbiome as a factor in understanding the response to probiotics and prebiotics. To understand the bigger picture, it’s necessary to also know how diet shapes the microbiome and determines probiotic and prebiotic response.” The paper explains that diet can directly influence factors such as gastric pH, the secretion of digestive enzymes, and the availability of energy for gut cells, which all shape the environment in which prebiotics and probiotics function.

The authors call for researchers across the globe to collect data on participants’ background diets as part of their future probiotic and prebiotic trials. The group made 10 key recommendations on the design, conduct and reporting of future probiotic and prebiotic clinical trials, including:

• Considering whether, and how, to harmonize the diet of your study population before the intervention.
• Giving precise instructions to participants on the dose and timing of the probiotic or prebiotic substance.
• Scheduling clinical trials to avoid holidays or other times when the dietary intake of the participants may be dramatically different from usual.
• Selecting a dietary assessment method that best answers the research question, for example for short-term or long-term studies.
• Rounding out the research team with a dietitian or nutrition researcher who has experience in dietary assessment and the gut microbiome.

The authors say that by accounting for the influence of diet, researchers may be able to unlock more personalized and effective approaches to improving health through prebiotic and probiotic interventions.