Evidence Summaries

The quality of evidence is downgraded by study limitations (unclear allocation concealment, blinding and incomplete outcome data in half of the trials).

A Cochrane review ¹ included 8 studies with a total of 258 subjects. Duration of the included studies was too short (1 to 26 weeks) to test the effect of salt restriction on endpoints such as mortality, cardiovascular events or chronic kidney disease (CKD) progression. There was a significant reduction in 24 hour sodium excretion associated with low salt interventions (range 52 to 141 mmol) ( MD -105.86 mmol/d, 95% CI -119.20 to -92.51; 8 studies, n=258, I²=51%). Reducing salt intake significantly reduced systolic blood pressure (MD -8.75 mm Hg, 95% CI -11.33 to -6.16; 8 studies, n=258, I²=0%) and diastolic blood pressure (MD -3.70 mm Hg, 95% CI -5.09 to -2.30; 8 studies, n=258,I²=0%). One study reported restricting salt intake reduced the risk of oedema by 56%. Salt restriction increased plasma renin activity and serum aldosterone. Antihypertensive medication dosage was significantly reduced with a low salt diet (RR 5.48, 95% CI 1.27 to 23.66; 2 studies, n=52, I²=0%). There was no significant difference in eGFR, creatinine clearance, serum creatinine, or body weight. Salt restriction significantly reduced urinary protein excretion in all studies that reported proteinuria as an outcome (4 trials, n=149), however data could not be meta-analysed.

References

1. McMahon EJ, Campbell KL, Bauer JD et al. Altered dietary salt intake for people with chronic kidney disease. Cochrane Database Syst Rev 2015;(2):CD010070.  [PMID:25691262]