The impact of botanical fermented foods on obesity, metabolic syndrome and type 2 diabetes: a systematic review of randomised controlled trials
Authors: Chan Miin , Larsen Nadja , Baxter Helen , Jespersen Lene , Ekinci Elif I , Howell Kate 
Published: December 2022

ABSTRACTObjectiveTo 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).DesignSystematic reviewData sourcesEmbase, MEDLINE, Cochrane CENTRAL and Google Scholar were searched with no language limits, from inception to August 31, 2022.Eligibility criteriaRandomised 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 synthesisTwo 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.ResultsThe 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.ConclusionIn 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 asBifidobacteriumand LAB, whilst reducing potential pathogens likeBacteroides. 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.EthicsEthical approval was not required as primary data was not collected.PROSPERO registration numberCRD42018117766STRENGTHS AND LIMITATIONS OF THIS STUDYTo the best of our knowledge, this is the first systematic review assessing RCTs of BFFs on metabolic, inflammatory, anthropometric and gut microbiota parameters in adults with obesity, T2DM, MetS or its components.Our search strategy adhered to the Cochrane review methodology and the PRISMA statement requirements.To ensure cultural inclusion and comprehensive up-to-date findings, our search started from inception to 31 August 2022, and had no language limits.ROB2, the most recent version of the Cochrane risk-of-bias tool, was used to assess the risk of bias in five domains covering the design, conduct and reporting of the included RCTs.Due to significant heterogeneity of BFF types, dosage, length of intervention and target populations, meta-analysis could not be conducted.