Diet Quality and Protein-Bound Uraemic Toxins: Investigation of Novel Risk Factors and the Role of Microbiome in Chronic Kidney Disease

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

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

14 Citations (Scopus)


Objective: This study aims to explore the associations between diet quality, uraemic toxins, and gastrointestinal microbiota in the chronic kidney disease (CKD) population. 

Methods: This is a baseline cross-sectional study of adults with CKD participating in a randomized controlled trial of prebiotic and probiotic supplementation. Dietary intake was measured using a seven-day diet history method, administered by a specialist dietitian. Diet quality was assessed using plant-based diet index (PDI) (overall PDI, healthy PDI, and unhealthy PDI), food group analysis, protein intake, fiber intake, and dietary protein-to-fiber ratio. Serum uraemic toxins (free and total; indoxyl sulfate and p-cresyl sulfate) were determined by ultraperformance liquid chromatography. Gastrointestinal microbiota richness, diversity, composition, and functional capacity were analyzed via metagenomic sequencing. 

Results: Sixty-eight adults [median age: 70 (interquartile range: 58-75) years, 66% male] with an estimated glomerular filtration rate of 34 ± 11 mL/min/1.73 m2 were included, with 40 participants completing the optional fecal substudy. Dietary fiber intake was associated with lower levels of total indoxyl sulfate, whereas the healthy plant-based diet index was associated with lower levels of free p-cresyl sulfate. A higher protein-to-fiber ratio was associated with an increased relative abundance of unclassified members of order Oscillospirales. Intake of vegetables and whole grains was correlated with Subdoligranulum formicile, whereas an unclassified Prevotella species was correlated with potatoes and food items considered discretionary, including sweet drinks, sweet desserts, and animal fats.

Conclusions: Diet quality may influence uraemic toxin generation and gut microbiota diversity, composition, and function in adults with CKD. Well-designed dietary intervention studies targeting the production of uraemic toxins and exploring the impact on gut microbiome are warranted in the CKD population. Keywords: Kidney disease; diet quality; gut microbiota; p-cresyl sulphate; indoxyl sulfate

Original languageEnglish
Pages (from-to)542-551
Number of pages10
JournalJournal of Renal Nutrition
Issue number5
Early online date12 Nov 2021
Publication statusPublished - Sept 2022
Externally publishedYes


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