The impact of botanical fermented foods on obesity, metabolic syndrome and type 2 diabetes: a systematic review of randomised controlled trials

Objective To assess whether botanical fermented food (BFF) consumption has an impact on cardiometabolic biomarkers or gut microbiota in adults with obesity, metabolic syndrome (MetS) or type 2 diabetes mellitus (T2DM). Design Systematic review Data sources Embase, MEDLINE, Cochrane CENTRAL and Google Scholar were searched with no language limits, from inception to August 31, 2022. Eligibility criteria Randomised controlled trials (RCTs) investigating the effects of BFFs on glucose, lipid, anthropometric, inflammatory and gut microbial parameters, in participants with obesity, MetS or T2DM. Data extraction and synthesis Two independent reviewers screened 6873 abstracts and extracted relevant data. Risk of bias (ROB) was assessed using the Cochrane Collaboration’s ROB2 tool. A qualitative, narrative synthesis was produced. Results The final review included 26 RCTs, with 31 reports published between 2001 and 2022. Significant (p<0.05) within-group and between-group changes in cardiometabolic outcome means were reported in 23 and 19 studies, respectively. Gut microbiota composition was assessed in four studies, with two finding significant between-group differences. No significant difference between groups of any measured outcomes was observed in five studies. There were 14 studies at low ROB; ten were of some concern; and two were at high ROB. Conclusion In 73% of included studies, BFF consumption by participants with obesity, MetS or T2DM led to significant between-group improvements in cardiometabolic outcomes, including fasting blood glucose, lipid profile, blood pressure, waist circumference, body fat percentage, and C-reactive protein. BFF consumption increased the abundance of beneficial gut bacteria, such as Bifidobacterium and LAB, whilst reducing potential pathogens like Bacteroides . To determine the clinical significance of BFFs as therapeutic dietary adjuncts, their safety, tolerability and affordability must be balanced with the limited power and magnitude of these preliminary findings. Ethics Ethical approval was not required as primary data was not collected. PROSPERO registration number CRD42018117766 STRENGTHS AND LIMITATIONS OF THIS STUDY ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement MC was supported by an Australian Government Research Training Program (RTP) Scholarship through the University of Melbourne, Australia. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The source data is available through the references cited in the paper. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present work are contained in the manuscript