HDCN Article Review/Hyperlink

Pedrini MT, Levey AS, Lau J, Chalmers TC, Wang PH

The effect of dietary protein restriction on the progression of diabetic and non-diabetic renal diseases: a meta -analysis

Ann Int Med (Mar) 124:627-632 1996

This is a meta-analysis to evaluate the efficacy of dietary protein restriction on the progression of renal disease in patients with diabetic and non-diabetic renal diseases. Only five randomized, controlled studies, with a mean length of follow-up of more than one year were included for non-diabetic renal disease (a total of 1413 patients). Five randomized controlled or non-randomized crossover design studies, with a mean length of follow-up of more than 9 months were included for insulin-dependent diabetic nephropathy (a total of 108 patients). Renal failure or death for non-diabetic renal disease, and the increase in urinary albumin level (more than 10% from baseline) or the decline in glomerular filtration rate or creatinine clearance (more than 1.2 ml/min per year) for diabetic nephropathy, were selected as the endpoints.

Random-effects model analysis indicated that dietary protein restriction (0.4-0.6 g/kg of body weight per day) significantly reduced the risk for renal failure or death (relative risk, 0.67 [95%CI, 0.50 to 0.89]) compared with usual diet in patients with non-diabetic renal disease. Dietary protein restriction (0.50-0.85g/kg of body weight per day) significantly slowed the increase in urinary albumin level or the decline in glomerular filtration rate or creatinine clearance (relative risk, 0.56 [95% CI, 0.40 to 0.77]) in patients with non-diabetic renal disease. This apparent beneficial effect of dietary protein restriction did not seem to be the result of an effect on blood pressure (diabetic and non-diabetic renal disease) or glycosylated hemoglobin level (diabetic renal disease only). In summary, dietary protein restriction effectively slows the progression of both diabetic and non-diabetic renal diseases.

Comment: This study has several limitations:
1) For non-diabetic renal diseases, the authors used pooled endpoints (renal failure or death), admittedly for the limited number of patients in each categories, and showed that dietary protein restriction significantly decreased the risk for renal disease progression. However, the use of patient death as the end point biases the results, since the patient can die without renal failure, and the beneficial relationship between dietary protein restriction and death is difficult to explain. Moreover, the exact number of patients who developed either renal failure or died is not specified.
2) Studies in patients with diabetic renal diseases included small numbers of patients, varied in design, and did not include renal failure as the end point. Thus, the results are inconclusive proof (as mentioned rightly by the authors).
3) Other potential risk factors related to renal disease progression, such as proteinuria (for non-diabetic renal diseases), underlying nephropathy, and dyslipidemia are lacking.
4) The possible harmful effects of dietary protein restriction on the nutritional status of patients with chronic renal disease are not evaluated.

Thus, I think we are awaiting still conclusive proof that a low protein diet is beneficial and safe in patients with diabetic and non-diabetic renal diseases. (Ziad A. Massy, M.D., Hopital Necker, Paris, France)

The abstract and full text article are available at the ACP Online site. abstract

The full text article is available at fulltext