Dietary counselling to reduce moderate sodium intake: effects on cardiovascular and renal biomarkers: primary findings of the COSIP and STICK phase II feasibility randomised controlled trials
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BACKGROUND: While low sodium intake (<2.3 g/day) is recommended, there is uncertainty about long-term feasibility and effects on cardiorenal biomarkers in populations with moderate intake. METHODS: In two phase IIb, feasibility, randomised, parallel, open-label, controlled, single-centre trials, individuals aged >40 years with stable blood pressure (BP), without heart failure or postural hypotension were randomised to intensive dietary counselling (target sodium intake <2.3 g/day) or usual care between March 2016 and July 2018. One trial included participants with chronic kidney disease (CKD); the other excluded those with CKD or cardiovascular disease. All participants received healthy eating advice. Primary outcomes were NT-pro B-type natriuretic peptide (NT-proBNP), high sensitivity troponin T (hsTnT), C-reactive protein (CRP), renin, aldosterone and, creatinine clearance (CrCl) at 2-years. These trials are registered with ClinicalTrials.gov, STICK trial (NCT02458248) and COSIP trial (NCT02738736). FINDINGS: 373 participants, with mean 24-h urine sodium 3.16 ± 1.47 g/day, were randomised to intervention (n = 187) or usual care (n = 186). At 3-months, the intervention reduced 24-h urine sodium (intervention -0.11 g/day, usual care +0.28 g/day, p = 0.003), BP (systolic -2.52 mmHg, p = 0.05; diastolic -1.92, p = 0.02) and increased renin (+33.35 mIU/L [95%CI 3.78-62.91]). At 2-years, the intervention significantly reduced self-reported salt use (p < 0.001), but not 24-h urine sodium (intervention -0.23 g/day, usual care +0.05 g/day, p = 0.47). At 2-years, there were no significant between-group differences in BP (systolic p = 0.66; diastolic p = 0.09), NT-proBNP (p = 0.68), hsTnT (p = 0.20), CRP (p = 0.56), renin (p = 0.52), aldosterone (p = 0.61), or CrCl (p = 0.68). INTERPRETATION: Among individuals with moderate sodium intake, intensive dietary counselling resulted in small short-term reductions in sodium intake and BP, but no significant effect on sodium intake, BP, or cardiorenal biomarkers at two years. Our trial suggests that it may not feasible to reduce sodium sustainably in those with a sodium intake around 3.0 g/day, through an intensive dietary counselling intervention. FUNDING: The STICK trial was funded by the Health Research Board of Ireland and the COSIP trial was funded by the European Research Council.