A randomized crossover trial of dietary sodium restriction in stage 3–4 CKD

Abstract

Background and objectives Patients with chronic kidney disease (CKD) are often volume expanded and hypertensive. Few controlled studies have assessed the effects of a sodium-restricted diet (SRD) in CKD. Design, setting, participants, & measurements We conducted a randomized crossover trial to evaluate the effect of SRD (target, 2 g sodium per day) versus usual diet on hydration status (by bioelectrical impedance spectroscopy) and blood pressure (BP) between May of 2009 and May of 2013. A total of 58 adults with stage 3–4 CKD were enrolled from two academic sites: University of Michigan (n=37) and University of North Carolina at Chapel Hill (n=21); 60% were men, 43% were diabetic, 93% were hypertensive, and mean age was 61 years. Participants followed SRD or usual diet for 4 weeks, followed by a 2-week washout period and a 4-week crossover phase. During the SRD, dieticians provided counseling every 2 weeks, using motivational interviewing techniques. Results Whole-body extracellular volume and calf intracellular volume decreased by 1.02 L (95% confidence interval [95% CI], 21.48 to 20.56; P,0.001) and 20.06 L (95% CI, 20.12 to 20.01; P=0.02), respectively, implying decreased fluid content on the SRD compared with usual diet. Significant reductions in urinary sodium (257.3 mEq/24 h; 95% CI, 281.8 to 232.9), weight (22.3 kg; 95% CI, 23.2 to 21.5), and 24-hour systolic BP (210.8 mmHg; 95% CI, 217.0 to 24.6) were also observed (all P,0.01). Albumin-to-creatinine ratio did not change significantly and mean serum creatinine increased slightly (0.1 mg/dl; 95% CI, 20.01 to 0.2; P=0.06). No period or carryover effects were observed. Results were similar when analyzed from phase 1 only before crossover, although P values were modestly larger because of the loss of power. Conclusions In this randomized crossover trial, implementation of SRD in patients with CKD stage 3–4 resulted in clinically and statistically significant improvement in BP and hydration status. This simple dietary intervention merits a larger trial in CKD to evaluate effects on major clinical outcomes.