Low-protein diet for diabetic nephropathy: a meta-analysis of randomized controlled trials.

BACKGROUND A low-protein diet (LPD) has been proposed for many years to delay the progression of diabetic nephropathy. However, the efficacy of an LPD with respect to renal outcome is disputed. OBJECTIVE We aimed to determine the effect of an LPD on renal function in patients with type 1 or 2 diabetic renal diseases by using a meta-analysis of randomized controlled trials. DESIGN Medline, EMBASE, and the Cochrane Central Register of Controlled Trials were searched. Eight studies met the inclusion criteria for our meta-analysis: a duration of >6 mo, use of a randomized control group, availability of outcome data for changes in glomerular filtration rate (GFR) or creatinine clearance rate (CCR), and albuminuria or proteinuria in patients with type 1 or 2 diabetic nephropathy. Data were combined by means of a fixed-effects model. Weighted mean differences (WMD) were calculated for the change in GFR or CCR, glycated hemoglobin (HbA(1c)), and serum albumin between the LPD and control groups. A random-effects model was also used to calculate the standardized mean difference for the change in urinary albumin excretion or proteinuria. RESULTS Overall, a change in WMD for GFR or CCR was not significantly associated with an LPD, but a decrease in WMD for HbA(1c) was significant in the LPD group (P = 0.005). Although the benefit of LPD therapy on proteinuria was significant (P = 0.003), great heterogeneity was observed. In a subgroup analysis, LPD resulted in lower serum albumin concentrations. CONCLUSION LPD was not associated with a significant improvement of renal function in patients with either types 1 or 2 diabetic nephropathy.