Sodium-Restricted Diet Improves Systolic Blood Pressure in Chronic Kidney Disease Patients

The consumption of a sodium-restricted diet significantly improved both blood pressure and hydration status in patients with chronic kidney disease.

In a study published in theClinical Journal of the American Society of Nephrology, participants devised their own meals based on counseling from dietitians who used motivational interview techniques rather than a diet of pre-prepared low sodium meals.

“While prior studies have documented the efficacy of dietary sodium restriction in reducing blood pressure in the general hypertensive population, few have explored this in the CKD population,” the authors wrote.

The study was a randomized, crossover trial including 58 adult patients with stage 3 or 4chronic kidney disease. Of all the participants 60% were male, 43% were diabetic, and 93% were hypertensive, with a mean age of 61 years.

The participants either followed a sodium restrict diet—–which was less than 2 g per day––or their usual diet for 4 weeks, followed by a 2-week washout period and a 4-week crossover phase.

During the sodium-restricted diet phase of the study, dieticians provided the participants with in-person counseling at baseline, week 2, and week 4, using motivational interview techniques. Additionally, dietitians also called patients at week 1 and week 3 to maintain motivation, assess compliance, and offer advice.

Adherence to the low-sodium diet was also assessed by 24-hour urinary sodium excretion, according to the study.

The primary outcome was defined as change in hydration status from baseline to 4 weeks. Secondary outcomes included 4-week changes from baseline in ambulatory blood pressure, albuminuria, and body weight.

The results of the study showed that patients on a low-sodium diet had a systolic blood pressure that was an average of 10.8 mm Hg lower after 4 weeks compared with the control group on their usual diet.

Whole-body extracellular volume decreased by 1.02 L in the treatment group compared with the control group. Additionally, urinary sodium was found to decrease by 57.3 mEg/hr, and body weight decreased by 2.3 kg.

“We found that reducing sodium in the diet helps to significantly reduce blood pressure and reduce the excess fluid retention that is common among patients with kidney disease,” said investigator Rajiv Saran, MD. “This does not require complicated pre-cooked meals and was simply based on common sense advice given by trained dietitians that helps patients understand what it takes to reduce salt in their diets and what the potential benefits are likely to be.”

There was no significant change observed in the albumin:creatinine ratio, and the mean serum creatinine increased slightly in the treatment group, according to the investigators.

“The intervention proved safe, although a slight increase in serum creatinine was observed,” the authors wrote. “This effect was more pronounced at the site where sodium-reduced diet adherence was greater. With decreases in extracellular volume and blood pressure, the slight rise in serum creatinine could relate to small reductions in intraglomerular pressure, analogous to the slight rise in serum creatinine following ACE inhibitor initiation.”

A limitation to the study was a violation in the randomization procedure at 1 of 2 study sites, which resulted in the overall results being predominately driven by results at the other site, according to the authors.

“Optimal blood pressure control remains a cornerstone of [chronic kidney disease] management,” the authors wrote. “In this randomized, crossover trial, we have demonstrated the feasibility and efficacy of dietary sodium restriction using motivational interviewing without invoking pre-prepared meals, in effecting meaningful improvements in both hydration status and blood pressure among patients with [chronic kidney disease]. The intervention was well tolerated and no clinically significant adverse outcomes were observed.”

The study authors concluded that bigger and longer-term clinical trials are needed to further examine and confirm these findings.