Salt hastens kidney function decline in autosomal dominant polycystic kidney disease
A study from the Netherlands indicated higher consumption of salt was associated with accelerated disease progression for patients with autosomal dominant polycystic kidney disease. This effect was not seen with higher protein intake.
According to Bart J. Kramers, MD, of the University of Groningen, and colleagues, limitations on salt intake are recommended for patients with chronic kidney disease, though data on protein restriction are more “controversial.”
Looking more specifically at patients with autosomal dominant polycystic kidney disease (ADPKD), they contended that data related to the impact of both salt and protein consumption on kidney function are “scarce.”
To this end, the researchers considered the association of these dietary factors with the rate of disease progression, collecting 24-hour urine samples from 589 patients with ADPKD (59% were women; mean age at baseline, 47 years; mean eGFR 64 mL/min/1.73m2; mean estimated salt intake, 9.1 g/day; mean protein intake, 84 g/day).
Participants were followed for a median of 4 years, with eGFR assessed a median of six times and 24-hour urine collected a median of five times.
The researchers found that while salt intake was significantly associated with an annual change in eGFR of -0.11, protein intake did not demonstrate an association with change in eGFR.
Noting that the effect of salt intake on eGFR was mediated by plasma copeptin, but not by systolic blood pressure, the researchers suggested salt intake may have “detrimental effects” by increasing vasopressin.
“This is the first study that shows an association between salt intake and eGFR slope in a cohort where early stage and later-stage ADPKD patients are both well represented,” they concluded. “Our finding that 1 gram of salt intake is associated with -0.11 mL/min/1.73m2 annual change in eGFR suggests that adherence to the current sodium restriction guidelines could significantly postpone end-stage kidney disease.”
“Based on our data,” they added, “there is no indication that protein restriction is beneficial.”