A shaker of salt can be found at almost every table — but new research is suggesting that people with kidney problems might want to give the mineral a second thought.
The new study examined patients with chronic kidney disease as they followed low- and high-sodium diets.
The researchers found that a reduced salt intake was associated with drops in blood pressure and improvement on several other markers for kidney health.
In chronic kidney disease (CKD), the kidneys are unable to perform their function of helping the body remove wastes and toxins. The National Kidney Foundation reports that eventually, CKD can cause heart problems too, like high blood pressure or an increased risk of heart disease.
According to the authors of this new study — who were led by Emma J. McMahon, PhD candidate at the University of Queensland in Brisbane, Australia — little is known about how sodium restriction might affect CKD patients.
McMahon and colleagues followed 20 CKD patients for several weeks. Fifteen of the patients (75 percent) were men and the average age was 68.5 years old.
Patients were advised to follow a low-sodium diet of 60 to 80 millimoles (mmol) per day for two weeks. One teaspoon of salt contains about 104 mmol of sodium.
Later, patients had a high-salt diet of 180 to 200 mmol per day for two weeks. During this period, patients continued to adhere to the low salt diet but received extra sodium through supplemental tablets.
A variety of measurements were taken after each portion of the study, including blood pressure, urine tests for protein and extracellular fluid volume. The study authors explained that an excess of fluids (measured through extracellular fluid volume) could be associated with cardiovascular events and an excess of protein in the urine can signal that the kidneys are not functioning effectively and are allowing key nutrients to pass through the body.
McMahon and colleagues found that during the low salt period, blood pressure was lowered by an average of 10/4 mmHg (millimeter of mercury, the unit used to measure blood pressure).
Extracellular fluid volume also dropped an average of 0.8 liters during the low salt period, and protein in the urine dropped from an average of 835 milligrams in 24 hours to 493 milligrams in 24 hours.
The study authors noted that the drop in blood pressure and extracellular fluid volume represented "... a considerable magnitude of change comparable with that expected from the addition of an antihypertensive medication."
The study was fairly small and more research is needed.
"Although studies with longer intervention times and larger sample sizes are needed to confirm these benefits, this study indicates that sodium restriction should be emphasized in the management of patients with CKD as a means to reduce cardiovascular risk and risk for CKD progression," McMahon and colleagues concluded.
The study was published November 7 in the Journal of the American Society of Nephrology.
Supplies and funding were provided by a number of organizations including Princess Alexandra Hospital, Kidney Health Australia, Fresenius Medical Care, Freedom Foods and Carman’s Fine Foods.