Altered dietary salt intake for people with chronic kidney disease

Background Salt intake shows great promise as a modifiable risk factor for reducing heart disease incidence and delaying kidney function decline in people with chronic kidney disease (CKD). However, a clear consensus of the benefits of reducing salt in people with CKD is lacking. Objectives This review evaluated the benefits and harms of altering dietary salt intake in people with CKD. Search methods We searched the Cochrane Renal Group's Specialised Register to 13 January 2015 through contact with the Trials' Search Co‐ordinator using search terms relevant to this review. Selection criteria We included randomised controlled trials (RCTs) that compared two or more levels of salt intake in people with any stage of CKD. Data collection and analysis Two authors independently assessed studies for eligibility and conducted risk of bias evaluation. Results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) and 95% CI for continuous outcomes. Mean effect sizes were calculated using the random‐effects models. Main results We included eight studies (24 reports, 258 participants). Because 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 CKD progression, changes in salt intake on blood pressure and other secondary risk factors were applied. Three studies were parallel RCTs and five were cross‐over studies. Selection bias was low in five studies and unclear in three. Performance and detection biases were low in two studies and unclear in six. Attrition and reporting biases were low in four studies and unclear in four. One study had the potential for high carryover effect; three had high risk of bias from baseline characteristics (change of medication or diet) and two studies were industry funded. There was a significant reduction in 24 hour sodium excretion associated with low salt interventions (range 52 to 141 mmol) (8 studies, 258 participants: MD ‐105.86 mmol/d, 95% CI ‐119.20 to ‐92.51; I2 = 51%). Reducing salt intake significantly reduced systolic blood pressure (8 studies, 258 participants: MD ‐8.75 mm Hg, 95% CI ‐11.33 to ‐6.16; I2 = 0%) and diastolic blood pressure (8 studies, 258 participants: MD ‐3.70 mm Hg, 95% CI ‐5.09 to ‐2.30; I2 = 0%). One study reported restricting salt intake reduced the risk of oedema by 56%. Salt restriction significantly increased plasma renin activ