High-protein diets increase eGFR in adults without chronic kidney disease across 22 randomized controlled trialsHigh protein diets may improve kidney function markers in adults

BACKGROUND: High-protein diets are widely prescribed for weight management and metabolic control, yet concerns persist regarding their impact on renal function, particularly due to diet-induced hyperfiltration. OBJECTIVE: We evaluated the effects of high-protein diets compared with normal- or low-protein (NPL) diets on renal function and body composition in adults without chronic kidney disease. METHODS: We systematically searched PubMed, Embase and the Cochrane Central Register of Controlled Trials from inception to May 2026 to identify randomised controlled trials comparing high-protein diets (typically ranging from approximately 25%-35% of total energy intake or ≥ 2.0 g/kg/day) with NPL diets in adults without chronic kidney disease. We defined estimated glomerular filtration rate (eGFR) and serum creatinine as primary outcomes. We evaluated body fat percentage, total fat mass and fat-free mass as secondary outcomes. We performed random-effects meta-analyses using restricted maximum likelihood estimation. We assessed risk of bias with the Cochrane RoB 2 tool and evaluated certainty of evidence using GRADE. RESULTS: We included 22 randomised controlled trials. High-protein diets increased eGFR compared with control diets (standardised mean difference 0.39, 95% confidence interval 0.09-0.69; I  = 74.9%). However, because most studies relied on creatinine-based estimates of renal function, these findings should be interpreted cautiously and may primarily reflect short-term hemodynamic adaptations associated with increased protein intake. High-protein diets did not significantly change serum creatinine (19 trials; n = 1044; standardised mean difference 0.08, 95% confidence interval -0.09 to 0.25; I  = 20.8%), without consistent biochemical evidence suggestive of renal injury. High-protein diets reduced body fat percentage and total fat mass, while they did not significantly affect fat-free mass. CONCLUSIONS: High-protein diets were associated with increases in eGFR without consistent biochemical evidence of renal injury in adults without chronic kidney disease. However, because most available studies were of relatively short duration and frequently relied on creatinine-based estimates of renal function, the long-term renal implications of these findings remain uncertain. TRIAL REGISTRATION: PROSPERO: CRD420251014114.