Reducing salt prevents kidney failure

Cutting down on salt intake can reverse the first physical signs that patients are developing kidney disease.

The study involved 120 rural Chinese villages that were randomised to a dietary salt reduction program that included education and the availability of a reduced-sodium salt substitute through village stores. After 18 months the urinary albumin levels were assessed in around 2000 people living in those communities.

The results showed that high urinary levels of albuminuria were lowered when people reduced their dietary salt intake.

Albumin is a normal component of blood, but its leakage into the urine can signal kidney damage and progression towards kidney failure. In addition, people with higher levels of albumin in urine are more at risk of having a heart attack or stroke.

In 2011-12, 1.3 million (or 7.7%) Australians aged 18 years and over had albuminuria. Rates of kidney disease are projected to rise in line with rises in the rates of diabetes forecast for the next decade.

“The medical community knows that albumin in the urine is associated with poor prognosis. Reducing salt intake effectively reduces the warning signs of higher urinary albumin that herald kidney and heart disease,” said Professor Meg Jardine from The George Institute for Global Health and The University of Sydney, who led the study.

“This study gives us a potential new method for improving health. Certain pharmaceutical agents lower urinary albumin and improve long-term kidney and cardiovascular outcomes and are recommended for many people with kidney disease.

“Dietary salt reduction achieves similar degrees of urinary albumin lowering. It may represent an approach to improving health above and beyond that achieved through pharmaceutical methods.”

Rates of stroke are particularly high in China but the global implications of this work are potentially profound.

The findings set the scene for a larger study that would conclusively link salt reduction with a lower rate of kidney disease. If confirmed, this will lead to a change of practice in the management of patients with albuminuria.

The research was presented at the 2014 American Society of Nephrology Renal Week.