sodium reduction

Reducing Sodium Intake Lowers BP in Patients With Kidney Disease

Reducing sodium in the diet helps to significantly lower blood pressure (BP) and reduce the excess fluid retention common among patients with chronic kidney disease (CKD), according to a new study.

Researchers conducted a randomized crossover trial to evaluate a sodium-restricted diet (SRD) (target <2g Na/day) vs. “usual diet” on hydration status (by bioelectrical impedance spectroscopy) and BP between May 2009 and May 2013. They enrolled 58 adults with stage 3-4 CKD from 2 academic sites: University of Michigan (n=37) and University of North Carolina (n=21), 60% of which were male, 43% diabetic, and 93% hypertensive.
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Participants followed SRD or usual diet for 4 weeks, followed by a 2-week washout period and a 4-week crossover phase. During SRD, dieticians provided counseling every 2 weeks using motivational interviewing techniques.

Whole-body extracellular volume and calf intracellular volume decreased by 1.02 L and -0.06 L, respectively, implying decreased fluid content on SRD compared to usual diet. They also observed significant reductions in urinary sodium, weight, and 24-hour systolic BP. Albumin:creatinine ratio did not change significantly, and mean serum creatinine increased slightly. They observed no period or carryover effects. Results were similar when analyzed from phase 1 only prior to crossover although p-values were modestly larger due to the loss of power.

This research is especially important because it highlights 3 main points, said lead study author Rajiv Saran, MBBS, MD, MS, MRCP, professor of medicine and epidemiology at University of Michigan in Ann Arbor:

  • Dietary sodium restriction to less than 2000 mg sodium per day is feasible to implement and practice in the real-world setting of the kidney clinic “without prescription of special pre-prepared meals—a cumbersome and not necessarily widely applicable strategy in routine clinical practice.”
  • The dietary intervention was safe for the patients with kidney disease.
  • The sodium restriction resulted in significant benefit to patients with moderately advanced kidney disease in terms of BP reduction and reduction of fluid/hydration status, both of which can improve cardiovascular morbidity and mortality in the long term. BP control also is important for slowing the rate of kidney disease progression.

“This simple dietary intervention merits a larger trial in CKD to evaluate effects on major clinical outcomes,” the researchers concluded.

—Mike Bederka

Reference:

Saran R, Padilla RL, Gillespie BW, et al. A randomized crossover trial of dietary sodium restriction in stage 3-4 chronic kidney disease [published online February 16, 2017]. Clin J Am Soc Nephrol. doi:10.2215/CJN.01120216.