Investigating the Effects of Synbiotic vs. Probiotic on Cardiometabolic Health: A Double-Blind Randomized Placebo Controlled Trial

INTRODUCTION: The human gut microbiome is a complex ecosystem of microorganisms which influences the health of the host. Dysbiosis, or an imbalance of the gut microbiome, has been associated with the development and occurrence of cardiovascular disease. The composition of the gut microbiome, and thus cardiovascular health, may be influenced by supplementation of prebiotics, probiotics, or synbiotics (pre- and probiotics). However, the effects of supplementation with probiotics, or synbiotics on the composition of the gut microbiome and subsequently, cardiometabolic health in relatively healthy individuals is not yet fully understood. PURPOSE: The purpose of this study was to evaluate the efficacy of short-term supplementation with synbiotic, probiotic, or placebo control over 30 days on cardiometabolic health in healthy individuals. METHODS: In a parallel design, sixty healthy males and females aged 18-60 years were recruited and randomly assigned to either the synbiotic (4 billion CFU/day probiotic + 2g xylooligosaccharide), probiotic (4 billion CFU/day + 2g maltodextrin), or placebo-control (collagen capsules+ 2g maltodextrin) supplementation for 30-days. Self-reported surveys (sleep, physical activity, gut health, and mood states), body weight and composition, blood pressure (central and peripheral), vascular stiffness, microvascular reactivity, and blood lipid levels were assessed pre- and post-intervention. Stool samples were acquired and analyzed for bacterial and fungal diversity (Chao and Shannon) using next gen sequencing-based 16s ribosomal RNA analysis. While food intake was ad libitum, dietary intakes were compared between groups at baseline and after 30-days. RESULTS: No differences were observed between groups at baseline (all, p >0.05). There were no significant interactions between time and condition for body composition, blood pressure and vascular stiffness, and glucose and lipid panels (all, p>0.05). There were no significant interactions of group over time for gut bacterial alpha diversity (Chao and Shannon, both p>0.05) or fungal alpha diversity (Chao and Shannon, both p>0.05). CONCLUSION: Short-term synbiotic or probiotic supplementation did not have any significant effects on gut bacterial or fungal diversity indices over placebo control; and thus, no effects were observed on cardiometabolic health in relatively healthy individuals over a one-month supplementation period. Longer term studies or those of higher doses of syn- or probiotics may be needed to elicit changes in the gut microbiome and corresponding cardiometabolic profile of relatively young healthy populations. Supported by Plexus Worldwide LLC (#2209-1044 to JAD, CJK, & SJI). The American Heart Association (AHA) has provided support to SJI (#24AIREA1247045). This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.