Authors' conclusions
Implications for practice
We found a strong case for the benefits of salt restriction in people with CKD. We found that reducing dietary salt considerably reduced BP in people with CKD. We found consistent evidence that dietary salt restriction reduced proteinuria in people with earlier stage (non‐dialysed, non‐transplanted) CKD by 34% to 36%. If such reductions were maintained long‐term, this may translate to clinically significant reductions in ESKD and cardiovascular events.
Reduced salt intake may increase symptomatic hypotension. Data were sparse for other types of adverse events.
Current evidence‐based clinical guidelines recommend a sodium intake target of less than 6 g of salt (100 mmol; 2300 mg sodium) per day for people with CKD, although achieving longer‐term adherence to this target can be challenging for patients without regular and ongoing support to improve their motivation, knowledge and prevent behaviour change decay. These findings were based on studies with intervention durations up to 6 months. There are ongoing studies with longer intervention durations which will strengthen the evidence for longer‐term effects.
Implications for research
We found that salt reduction in people with CKD reduced BP considerably and consistently reduced proteinuria over a time‐frame of up to 6 months. We found a critical evidence gap in long‐term effects of salt restriction in people with CKD that meant we were unable to determine the direct effects of sodium restriction on critical outcomes such as death and progression to ESKD. If the reductions we found in short‐term studies could be maintained long‐term, these benefits may translate to clinically significant reductions in ESKD incidence and cardiovascular events. Research into longer‐term effects of dietary sodium restriction for people with CKD is warranted, along with investigation of adherence to a low salt diet.
Despite consistent data from observational and non‐randomised studies showing that salt restriction reduced fluid volume in people with CKD, high quality RCTs are lacking. Further research on the effect of salt restriction on other cardiac and vascular abnormalities such as arterial stiffness, left ventricular hypertrophy, inflammation and oxidative stress is warranted.
Future studies investigating salt restriction should employ methods that limit risk of bias due to dietary confounders where possible and should take care to adequately measure dietary intake of not only sodium, but other nutrients that may confound study results. Research into long‐term adherence to a sodium‐restricted diet may assist in translating these results into a practical setting.
