Cardiovascular disease is a leading cause of death and disability worldwide, and blood pressure is a leading determinant of this risk. To date, strategies for blood pressure lowering have focused on drug treatment but dietary interventions such as reducing sodium intake and increasing potassium intake may also be effective. Such interventions may be particularly suitable for low- and middle-income countries in which significant dietary changes may be more easily achieved. This study will test the effect of a salt substitute on blood pressure, among individuals at high-risk from cardiovascular disease in Northern China.

This randomised trial will clearly identify whether a low-sodium, high-potassium salt-substitute is a feasible means of lowering blood pressure in high-risk individuals in rural China. The randomised design and the large size (n=600) will ensure that the results are reliable and precise. The 12-month duration will address the long-term practicability of the intervention strategy. The study is being conducted because salt-substitute-based blood pressure lowering may be particularly appropriate for rural populations in low- and middle-income countries. First, sodium intake is often very high. Second, the salt-substitute can be easily incorporated into the diet because most food is prepared and eaten at home. Third, the intervention can be provided at very low cost.

Comparisions: Low sodium high potassium salt (65% sodium chloride, 25% potassium chloride, 10% magnesium sulphate) compared to normal salt (100% sodium chloride).

Inclusion Criteria:

Participant inclusion will be based upon the presence of:

• A doctor-confirmed high risk of future vascular disease defined as a history of any one of:

  • Stroke or transient ischaemic attack
  • Hospitalisation for management of any acute coronary syndrome
  • Surgery or angioplasty for peripheral vascular disease
  • Treated diabetes and age 55 years or older
  • Systolic blood pressure >160mmHg

• Estimated daily sodium intake of 260mmol/24hrs (about 15g/24hrs of NaCl) or above and expectation that at least 50% of daily dietary salt intake can be replaced with the salt-substitute. This will be estimated through interview of the potential participant and the individual responsible for daily food preparation (if this is not the patient) using a structured questionnaire.

• Provision of informed consent

Exclusion Criteria:

Potential participants will be excluded if:

• they are on potassium-sparing medication
• there is an established history of significant renal impairment that would preclude the use of the salt-substitute in the opinion of the responsible physician.
• there is any reason why either the salt-substitute or normal salt are definitely indicated or definitely contra-indicated.