The effect of protein restriction on albuminuria in patients with type 2 diabetes mellitus: a randomized trial

BACKGROUND: A randomized trial was conducted to assess whether protein restriction helps to delay the onset of renal disorders in type 2 diabetic patients. METHODS: Included in the trial were 121 type 2 diabetic patients with microalbuminuria or at least detectable albuminuria, or diabetes of duration > or =5 years. The experimental (39 male/19 female) and control group (35 male/28 female) received counselling on protein restriction and the usual dietary advice, respectively. The outcome measure was albuminuria (mg/24 h). Results. After 6 months in experimental and control groups the change in protein intake was -0.05+/-0.21 and +0.03+/-0.19 g/kg (P = 0.02), and in albuminuria -14% and +11% (P = 0.01), respectively. After 12 months, the differences between the experimental and the control group with respect to both protein intake and albuminuria had decreased. At 6 and 12 months, respectively, albuminuria was 28% (P<0.001) and 18% (P = 0.08) lower in the experimental than the control group. The effect in normoalbuminuric patients did not differ from that in microalbuminuric patients. In the experimental group, blood pressure, HbA1c and body weight decreased; in the control group, such decreases were less or absent. Dose-response analysis showed that a 0.10 g/kg change at 6 months in the intake of protein, of animal protein in particular, was related to an 11.1% change in albuminuria (P<0.005). Combining the intakes at 6 and 12 months suggested a percentage change of 9.1%. CONCLUSIONS: Substantial protein restriction in primary care, type 2 diabetic patients with no nephropathy is barely feasible. However, even a small reduction has a substantial and potentially beneficial effect on albuminuria.