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Protein and Kidney Health
**Protein and Kidney Health** describes the relationship between dietary protein intake and kidney (renal) function — specifically the long-standing question of whether eating more protein harms the kidneys.
Effect on healthy kidneys
In adults with healthy kidneys, higher protein intake has not been shown to impair renal function. A 2018 systematic review and meta-analysis of 28 trials including 1,358 participants found that the change in glomerular filtration rate (GFR) did not differ between higher-protein and lower- or normal-protein diets (standardized mean difference 0.11; 95% CI −0.05 to 0.27; P = 0.16) (Devries et al., The Journal of Nutrition, 2018, PMID 30383278). High protein was defined as at least 1.5 g/kg body weight, at least 20% of energy, or at least 100 g per day.
A separate 2018 review of 26 studies reached the same conclusion: among the 13 randomized trials that measured GFR, 8 reported higher GFR with increased protein, but all values remained consistent with normal kidney function; most trials lasted under six months (Advances in Nutrition, 2018, PMID 30032227). An umbrella review conducted for the German Nutrition Society found no evidence that higher protein intake specifically triggers kidney stones or kidney disease (European Journal of Nutrition, 2023, PMID 37133532). A one-year crossover study in 14 resistance-trained men consuming 2.51–3.32 g/kg/day reported no harmful effects on kidney function (Journal of Nutrition and Metabolism, 2016, PMID 27807480).
Existing chronic kidney disease
In people already diagnosed with chronic kidney disease (CKD), the relationship reverses. In this population, dietary protein restriction is used to slow the progression of kidney disease. The 2020 KDOQI guideline from the National Kidney Foundation recommends that metabolically stable adults with CKD stages 3–5 not on dialysis and without diabetes restrict protein to 0.55–0.60 g/kg ideal body weight per day (American Journal of Kidney Diseases, 2020). The earlier NIDDK-funded Modification of Diet in Renal Disease (MDRD) Study tested low-protein (0.58 g/kg/day) and very-low-protein (0.28 g/kg/day plus a keto acid–amino acid supplement) diets against usual intake in patients with reduced GFR.
Origin of the concern
The belief that protein strains healthy kidneys is widespread but not supported by controlled data. The International Society of Sports Nutrition position stand notes that it is “often erroneously reported… that a chronically high protein intake… may result in unnecessary metabolic strain on the kidneys leading to impaired renal function.” The confusion appears to arise from extending advice meant for diagnosed kidney disease to the general population — one of the misunderstandings addressed in common protein powder problems. A high-protein diet is typically defined as one in which 40% or more of total daily calories come from protein.
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