Summary:
Fermented foods have been consumed for thousands of years. They contain beneficial microorganisms and bioactive compounds that may influence gut health, immune function, and the gut microbiota. Increasing interest in fermented foods has emerged alongside research suggesting that modern Western diets, which are high in processed foods and lower in naturally fermented products, may contribute to gut microbiota imbalance and chronic health conditions. This systematic review and meta-analysis investigated whether fermented food consumption improves gastrointestinal wellbeing in healthy adults. The paper specifically looked at common gastrointestinal symptoms such as bloating, constipation, abdominal discomfort, flatulence, bowel movement frequency, stool consistency, and intestinal transit time. A total of 25 studies involving 4,328 participants were included, with 19 randomised controlled trials used. The findings indicated that fermented food consumption was associated with improvements in several gastrointestinal outcomes. Participants showed increased bowel movement frequency, improved stool consistency, reduced constipation, faster intestinal transit time, and reductions in symptoms such as bloating, abdominal discomfort, bowel sounds, and flatulence. The study also discussed potential mechanisms underlying these effects, including modulation of the gut microbiota and the delivery of probiotics, prebiotics, and other bioactive compounds through fermented foods. This study concluded that fermented foods may support gastrointestinal function and improve common digestive symptoms in healthy adult populations.
Abstract:
Objective: In recent years, the consumption of fermented foods (FFs) has been linked with gastrointestinal health and wellbeing. Here, we systematically review and meta-analyse the currently available evidence relating to this as part of the COST Action PIMENTO and guided by the European Food Safety Authority (EFSA) health claim dossiers.Methods: MEDLINE, Scopus and Cochrane CENTRAL bibliographic libraries were searched for relevant literature up to 31st January 2025. All eligible studies were included for narrative review as per EFSA guidelines, but only randomised controlled trials (RCTs) were considered for meta-analyses. Risk of bias, mechanisms of action, bioactive compounds and safety were additionally discussed. Data was pooled using mean difference (MD)/standardized MD for continuous data and relative risk (RR) for dichotomous data. Certainty of evidence was evaluated through GRADE assessment.Results: A total of 25 studies (19 RCTs included in meta-analysis) with 4,328 participants were included in the systematic review. Meta-analysis demonstrated the beneficial impact of FF consumption on frequency of bowel movements (MD 0.60, CI 0.04, 1.16, p = 0.04, I2 = 74%), stool consistency (Bristol Stool Form Scale) (MD 0.25, CI 0.03, 0.47, p = 0.03, I2 = 72%), gastrointestinal symptoms (SMD −0.60, CI −1.05, −0.15, p = 0.009, I2 = 90%) and intestinal transit time (−13.65 CI −21.88, −5.43, p = 0.001, I2 = 95%), among others. Certainty of evidence was highly variable and mostly low.Conclusion: Our analysis suggests that FF consumption beneficially impacts the frequency of bowel movements, stool consistency, incidence of hard stools, intestinal transit time, abdominal symptoms, bloating, borborygmi, flatulence and degree of constipation.
Article Publication Date: 10/10/2025
DOI: 10.3389/fnut.2025.1668889
