Impact of Probiotics, Prebiotics and Synbiotics Supplementation in Chronic Kidney Disease: A Comprehensive Review of Clinical Trials

Chronic kidney disease (CKD) is a progressive condition associated with metabolic disturbances, systemic inflammation, and the accumulation of gut-derived uremic toxins. Increasing evidence highlights the role of gut microbiota dysbiosis in the progression of CKD through the gut–kidney axis. Consequently, microbiome-targeted nutritional strategies, including probiotics, prebiotics, and synbiotics, have emerged as promising complementary approaches to modulate intestinal microbial composition and metabolic functions. This review summarizes and critically evaluates the current clinical evidence regarding the use of these interventions in CKD patients. Clinical studies indicate that supplementation with probiotics, prebiotics, and synbiotic formulations may promote beneficial shifts in the composition of the gut microbiota, enhance saccharolytic fermentation, and increase the production of short-chain fatty acids (SCFAs). These changes have been associated with reduced circulating levels of gut-derived uremic toxins such as indoxyl sulfate and p-cresyl sulfate, as well as with the attenuation of systemic inflammation and oxidative stress. However, available trials remain heterogeneous in terms of study design, probiotic strains, prebiotic substrates, dosing regimens, and patient populations, and are frequently limited by small sample sizes and short intervention durations. As a result, evidence for improvements in renal function and long-term clinical outcomes remains inconclusive. While synbiotics may offer theoretical advantages by combining microbial supplementation with targeted substrates that support microbial growth and metabolic activity, current evidence does not consistently demonstrate superior clinical efficacy. Overall, these interventions often improve surrogate biomarkers, but their effects on renal function and hard clinical outcomes remain uncertain. Larger, longer-duration multicenter randomized controlled trials with standardized formulations are needed to establish their clinical utility and to better elucidate microbiota–host interactions in CKD. Advancing this field may support the development of personalized microbiome-based therapeutic strategies aimed at modulating the gut–kidney axis and ultimately improving clinical outcomes in CKD patients.