Lowering salt intake improves heart and kidney health of chronic kidney disease patients

November 07, 2013

Washington, DC (November 7, 2013) -- Reducing salt intake provides clear benefits for the heart and kidney health of patients with chronic kidney disease, according to a study appearing in an upcoming issue of the Journal of the American Society of Nephrology (JASN). The findings point to the power of salt restriction in potentially prolonging kidney disease patients' lives.

Excessive salt intake is consistently linked to increased risk of heart disease and worsening kidney function. People with chronic kidney disease (CKD) may be particularly susceptible to salt's detrimental effects due to the kidney's important role in controlling salt balance and their increased risk of dying from heart disease. Until now, though, the effect of salt restriction in these patients has not been well explored.

The LowSALT CKD study represents the first blinded randomized controlled trial comparing a high vs low salt intake in people with CKD. During the study, Emma McMahon (PhD candidate, University of Queensland, in Australia) and her colleagues, led by principal investigator Katrina Campbell, PhD (Princess Alexandra Hospital, in Australia) compared the effects of a high salt diet (180 to 200 mmol/day) vs a low salt diet (60 to 80 mmol/day) maintained for two weeks each in a random order in 20 patients with CKD. (Dietary guidelines recommend limiting sodium to less than 100 mmol--which is 2300 mg or one teaspoon--per day.) The team measured various parameters related to heart and kidney health, including change in extracellular fluid volume, blood pressure, and protein in the urine.

The researchers found that on average, low salt intake reduced excess extracellular fluid volume by 1 liter, lowered blood pressure by 10 /4 mm Hg, and halved protein excretion in the urine, without causing significant side effects.

"These are clinically significant findings, with this magnitude of blood pressure reduction being comparable to that expected with the addition of an anti-hypertensive medication and larger than effects usually seen with sodium restriction in people without CKD," said McMahon. She was particularly impressed with the 50% reduction in protein excretion in the urine. "If maintained long-term, this could reduce risk of progression to end-stage kidney disease--where dialysis or transplant is required to survive--by 30%."

The findings suggest that salt restriction is an inexpensive, low-risk and effective intervention for reducing cardiovascular risk and risk of worsening kidney function in people with CKD. "If these findings are transferable to the larger CKD population and shown to be sustainable long-term, this could translate to markedly reduced risk of cardiovascular events and progression to end-stage kidney disease, and it could generate considerable health-care savings," said Dr. Campbell.

In an accompanying editorial, Cheryl Anderson, PhD, and Jochim Ix, MD (University of California San Diego School of Medicine) commended the researchers for providing important clinical trial data in support of current clinical practice consensus guidelines, noting that "this study makes us cautiously optimistic." They added that larger studies with longer follow-up specifically designed and carried out in CKD populations are needed to help inform recommendations to both individual patients and policymakers.
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Highlights Study co-authors include Judith Bauer, PhD, Carmel Hawley, FRACP, PhD, Nicole Isbel, FRACP, PhD, Michael Stowasser, FRACP, PhD, David Johnson, FRACP, PhD, and Katrina L. Campbell, PhD.

Disclosures: This study was funded by research grants from the Princess Alexandra Hospital and Kidney Health Australia. The authors acknowledge Fresenius Medical Care for providing the body composition monitor for fluid measurement; Freedom Foods, Norco, Real Foods, Carman's Fine Foods, Sanitarium Health & Wellbeing Company, Rosella, and Diego's for donating food for the trial; Dr. Eduardo Pimenta for providing consultation on the design of the trial; the study nurse, Rachael Hale, for serving as the trial coordinator; Dr. Paul Taylor (University of Queensland) for providing the aldosterone assay; and the Princess Alexandra Hospital Renal Outpatient Department for providing organizational support. Emma McMahon is funded by an Australian Postgraduate Association scholarship through University of Queensland. Katrina Campbell is a current recipient of a Queensland Government Health Research Fellowship and Lions Senior Medical Research Fellowship. David Johnson is a current recipient of a Queensland Government Health Research Fellowship. The authors report no other financial disclosures or conflict of interest.

The article, entitled "A randomized trial of dietary sodium restriction in chronic kidney disease," will appear online at http://jasn.asnjournals.org/ on November 7, 2013, doi: 10.1681/ASN2013030285.

The editorial, entitled "Sodium Reduction in CKD: Suggestively Hazardous or Intuitively Advantageous?" will appear online at http://jasn.asnjournals.org/ on November 7, 2013, doi: 10.1681/ASN.2013090923.

The content of this article does not reflect the views or opinions of The American Society of Nephrology (ASN). Responsibility for the information and views expressed therein lies entirely with the author(s). ASN does not offer medical advice. All content in ASN publications is for informational purposes only, and is not intended to cover all possible uses, directions, precautions, drug interactions, or adverse effects. This content should not be used during a medical emergency or for the diagnosis or treatment of any medical condition. Please consult your doctor or other qualified health care provider if you have any questions about a medical condition, or before taking any drug, changing your diet or commencing or discontinuing any course of treatment. Do not ignore or delay obtaining professional medical advice because of information accessed through ASN. Call 911 or your doctor for all medical emergencies.

Founded in 1966, and with more than 14,000 members, the American Society of Nephrology (ASN) leads the fight against kidney disease by educating health professionals, sharing new knowledge, advancing research, and advocating the highest quality care for patients.

American Society of Nephrology

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