Nephrol Dial Transplant Vol. 19 No. 10 © ERA-EDTA 2004; all rights reserved
Letter
High protein diets may be hazardous for the kidneys
Sir,With the promise of rapid weight loss and better health, many patients are turning to high protein, low carbohydrate diets. ‘Low carb’ diet books are topping the New York Times Bestseller lists week after week, and are being touted as quick fix solutions to today's epidemics of obesity and type 2 diabetes. It must be acknowledged that these diets improve weight, sugars and cholesterol in the short term, but at what risk for a patient with renal disease?
From a nephrologist's point of view, there are two major concerns raised by such high protein, low carbohydrate diets. The first is worsening of proteinuria in patients with renal disease and the second is the development of nephrolithiasis in otherwise healthy people. Diabetic nephropathy is the leading cause of end-stage renal disease (ESRD) worldwide. Weight loss and improved glycaemic control are critical to attenuation of renal disease progression in these patients, but a highly significant predictor of progression is proteinuria [1,2]. Many animal and human studies of diabetic and other renal diseases have demonstrated that high protein diets exacerbate proteinuria and accelerate renal disease progression [3,4]. In addition, diets with high sodium and purine intakes are associated with increased risk of nephrolithiasis [5]. The current emphasis on high protein, low carbohydrate diets poses a dilemma: patients may benefit from weight loss and improved metabolic parameters but, if the potential cost is more rapid progression towards ESRD or the development of kidney stones, is the trade-off worth it?
We suggest that renal patients should be referred to a registered dietitian prior to considering these diets, and that meal plans should be carefully ‘tailored’ to meet individual needs. To maximize benefit and minimize potential harm, food choices should be modified to include low sodium, lower protein (0.8–1 g/kg/day) options, avoidance of processed foods, focus on more healthy fats, gradual inclusion of ‘good’ carbohydrates and adequate hydration.
At present, long-term data on cardiovascular and renal outcomes in patients following high protein, low carbohydrate diets are lacking. Until we have evidence that the benefits in terms of weight loss, glycaemic control and lipids outweigh potential adverse renal consequences, we suggest that physicians exercise caution in encouraging patients with renal disease to follow these diet plans without appropriate supervision.
Conflict of interest statement. None declared.
Brigham and Women's Hospital1 Nephrology2 Clinical Nutrition Boston, MA USA Email: vluyckx{at}partners.org
References
- Brenner BM. Retarding the progression of renal disease. Kidney Int 2003; 61: 370–378
- Ruggenenti P, Schieppati A, Remuzzi G. Progression, remission, regression of chronic renal diseases. Lancet 2001; 357: 1601–1608[CrossRef][Web of Science][Medline]
- Hebert L, Wilmer W, Falkenhain M, Ladson-Wofford S, Nahman N, Rovin B. Renoprotection: one or many therapies? Kidney Int 2001; 59: 1211–1226[CrossRef][Web of Science][Medline]
- Levey A, Greene T, Beck GJ et al. Dietary protein restriction and the progression of chronic renal disease: what have all the results of the MDRD study shown? J Am Soc Nephrol 1999; 10: 2426–2439
[Abstract/Free Full Text] - Coe F, Parks J, Asplin J. The pathogenesis and treatment of kidney stones. N Engl J Med 1992; 327: 1141–1152[Web of Science][Medline]
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  A. H. Manninen High-protein diets are not hazardous for the healthy kidneys Nephrol. Dial. Transplant., March 1, 2005; 20(3): 657 - 658. [Full Text] [PDF]
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V. A. Luyckx and T. A. Mardigan Reply Nephrol. Dial. Transplant., March 1, 2005; 20(3): 658 - 658. [Full Text] [PDF]
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