Dietary Fibre and Chronic Kidney Disease: A Systematic Review of Effects on Inflammation, Uraemic Toxins, Nutritional Status, Kidney Function, and Gut–Liver–Kidney Axis Mechanisms

Background: Dietary fibre has been increasingly recognised for its potential role in modulating inflammation, gut-derived uraemic toxins, nutritional status, and kidney-related outcomes in chronic kidney disease (CKD), particularly through mechanisms involving the gut–liver–kidney axis. While nutritional management in CKD has traditionally focused on protein intake, despite growing evidence supporting soluble and insoluble types, the role of dietary fibre remains insufficiently reflected in clinical guidelines. Objective: This systematic review evaluated the effects of dietary fibre intake on inflammatory markers, gut-derived uraemic toxins, nutritional status, kidney function, and mechanistic pathways relevant to gut–liver–kidney axis among CKD patients. Methods: PubMed, Scopus and Medline Complete were searched for observational and interventional human studies. Review articles and animal studies were excluded. A total of 45 met eligibility criteria. Risk-of-bias (RoB) was assessed using domain-based tools, and findings were synthesised narratively across predefined outcome domains. Results: Higher fibre intake was generally associated with reductions in interleukin-6 (IL-6) and selective improvements in inflammatory tone including Tumor Necrosis Factor alpha (TNF-α), while effects on C-reactive protein (CRP) varied. Several fermentable fibres were frequently linked with reduced gut-derived uraemic toxins, including indoxyl sulphate (IS), p-cresyl sulphate (pCS), and less consistently trimethylamine-N-oxide (TMAO). Nutritional markers such as albumin, BMI and overall diet quality were typically maintained or improved. Kidney function was stable across short-term interventions, with suggestions of slower decline in longer studies incorporating fibre-rich dietary patterns. Mechanistic studies frequently reported increased saccharolytic activity and favourable changes in fermentation profiles. Despite growing evidence, soluble fibre remains an underrepresented component in CKD dietary guidelines, warranting further high-quality interventional studies to confirm its therapeutic potential.