Synbiotics easing renal failure by improving gut microbiology ii (Synergy ii): A feasibility randomized controlled trial

Catherine McFarlane, Rathika Krishnasamy, Tony Stanton, Emma Savill, Matthew Snelson, Gabor Mihala, Jaimon T. Kelly, Mark Morrison, David W. Johnson, Katrina L. Campbell

Research output: Contribution to journalArticleResearchpeer-review

23 Citations (Scopus)


Synbiotics have emerged as a therapeutic strategy for modulating the gut microbiome and targeting novel cardiovascular risk factors, including uremic toxins indoxyl sulfate (IS) and p-cresyl sulfate (PCS). This study aims to evaluate the feasibility of a trial of long-term synbiotic supplemen-tation in adults with stage 3–4 chronic kidney disease (CKD). Adult participants with CKD and estimated glomerular filtration rate (eGFR) of 15–60 mL/min/1.73 m2 ) were recruited between April 2017 and August 2018 to a feasibility, double-blind, placebo-controlled, randomized trial of synbiotic therapy or matched identical placebo for 12 months. The primary outcomes were recruitment and retention rates as well as acceptability of the intervention. Secondary outcomes were treatment adherence and dietary intake. Exploratory outcomes were evaluation of the cardiovascular structure and function, serum IS and PCS, stool microbiota profile, kidney function, blood pressure, and lipid profile. Of 166 potentially eligible patients, 68 (41%) were recruited into the trial (synbiotic n = 35, placebo n = 33). Synbiotic and placebo groups had acceptable and comparable 12-month retention rates (80% versus 85%, respectively, p = 0.60). Synbiotic supplementation altered the stool micro-biome with an enrichment of Bifidobacterium and Blautia spp., resulting in a 3.14 mL/min/1.73 m2 (95% confidence interval (CI), −6.23 to −0.06 mL/min/1.73 m2, p < 0.01) reduction in eGFR and a 20.8 µmol/L (95% CI, 2.97 to 38.5 µmol/L, p < 0.01) increase in serum creatinine concentration. No between-group differences were observed in any of the other secondary or exploratory outcomes. Long-term synbiotic supplementation was feasible and acceptable to patients with CKD, and it modified the gastrointestinal microbiome. However, the reduction in kidney function with synbiotics warrants further investigation.

Original languageEnglish
Article number4481
Number of pages16
Issue number12
Publication statusPublished - Dec 2021


  • Gastrointestinal microbiome
  • Indoxyl sulfate
  • Kidney disease
  • P-cresyl sulphate
  • Randomized controlled trial
  • Synbiotic

Cite this