Dietary Interventions Modulating Gut Microbiota and Cardiometabolic Diseases – a Systematic Review of Human Clinical Trials

Abstract

Objective: Cardiometabolic diseases (CMD) have shared properties and causes. Insulin resistance is a risk factor and characteristic of CMD and has been suggested to be modulated by gut microbiota (GM) derived plasma metabolites. As diet is the most important modulator of GM, we performed a systematic review of the literature to assess if CMD can be modulated by dietary interventions targeting GM composition. Design: A systematic review of the literature for clinical studies was performed on Ovid Medline and Ovid Embase which resulted in 4444 unique articles and 21 studies m et al. l inclusion criteria. Included studies were assessed for bias assessment and results from studies were qualitatively analysed to find similarities and general patterns of intervention effects. Results: Fifteen randomized controlled trials (RCT) and six non-randomized clinical trials were included. Interventions and methods used were different between studies. Overall bias was high in all studies and RCT had high risk of selection of published results, this was mainly due to the absence of prepublished analysis plans. In general, most dietary interventions changed the GM composition but no consistent effect could be found. Due to the high heterogeneity of study characteristics and design no meta-analysis could be performed. We propose a four-step process to reduce selection bias of published results and improve methodological quality of microbiome studies. Conclusions: Dietary interventions modulate GM composition and most studies have a high risk of bias due to the used methods. To address this, future studies should follow the initial four-step approach for registration as proposed in this study. Funding: MW is supported by a CVON INCONTROL-II grant (2018-27),. IA is supported by a JPI HDHL MICRODIET grant (5290510105). MN is supported by a ZONMW VICI grant 2020[09150182010020]. HH is supported by a Senior Fellowship of the Dutch Diabetes Research Foundation (2019.82.004). Declaration of Interest: M Nieuwdorp is member of the Scientific Advisory Board of Caelus Health, the Netherlands and Kaleido Biosciences, USA. However, none of these conflicts of interest bear any relevance to the current content of the paper. All other authors have nothing to declare.