Clarifying Optimal Sodium Intake Project

Inclusion Criteria: * Age 40 years or older * Systolic blood pressure \<160mmHg and diastolic blood pressure \<95mmHg on three office blood pressure readings at time of screening and confirmed by a study ABPM before randomization of \<150/90mmHg * No change in anti-hypertensive or diuretic medications (including dose) for 3 months before screening visit * Consumption of moderate sodium intake at screening, defined as an estimated daily sodium intake of \>2.3/day estimated from food frequency questionnaire (FFQ) * Self-reported willingness to modify dietary intake over sustained period, and adhere with directed recommendations over 2 years. * Signed written informed consent Exclusion Criteria: * Known chronic kidney disease (CKD) or most recent eGFR ≤60ml/min/1.73m2 * Participants who are ineligible for COSIP based on their eGFR will be approached about entering the ongoing Sodium Intake in Chronic Kidney Disease (STICK) trial. * Previous cardiovascular disease: * Myocardial infarction * Previous percutaneous coronary intervention (PCI) or percutaneous transluminal coronary angioplasty (PTCA) * Stroke (previous transient ischaemic attack \[TIA\] is not an exclusion criterion) * Medical diagnosis known to be associated with abnormal renal sodium excretion, including the following: * Bartter syndrome * SIADH * Diabetes insipidus * Serum sodium \<125mmol * Severe heart failure defined as NYHA Class III/IV OR left ventricular ejection fraction (LVEF) ≤30% * High-dose loop or thiazide diuretic therapy, exceeding a total daily dose of frusemide 80mg, bumetanide 2mg, hydrochlorothiazide 50mg, bendroflumethiazide 2.5mg, indapamide 2.5mg, metolazone 2.5mg or the use of both a loop and thiazide diuretic * Unable to follow educational advice of the research team * Prescribed high-salt diet, low-salt diet or sodium bicarbonate * Symptomatic postural hypotension or receiving treatment for postural hypotension * Current or recent use (within one month) of immunosuppressive medications including tacrolimus, cyclosporine, azathioprine or mycophenolate mofetil * Pregnancy or lactation * Unable to comply with 24-hour urinary collections, or medical condition making collection of 24-hour urinary collection difficult (e.g. severe urinary incontinence) * Participant unlikely to comply with study procedures or follow-up visits due to severe comorbid illness or other factor (e.g. inability to travel for follow-up visits, drug or alcohol misuse) in the opinion of the research team * Cognitive impairment defined as a known diagnosis of dementia or inability to provide informed consent due to cognitive impairment in the opinion of the investigator * Body Mass Index (BMI) \<20 kg/m2 or BMI\>40 kg/m2 * Participating in another clinical trial or previous allocation in this study