Salt ALTernatives Study (SALTS): A smartphone app and dietary alternative salt to lower blood pressure for adults with high blood pressure

The intervention is designed to lower blood pressure and includies two components: (1) a smartphone application (app) called SaltSwitch, and (2) a dietary alternative salt. The SaltSwitch app helps users to select lower salt packaged foods by enabling them to scan the barcode of a packaged food and receive an immediate, interpretive traffic light nutrition label on-screen plus suggestions for lower salt alternatives. Users can also directly compare the salt content and healthiness of two or more food products. The dietary alternative salt is a blend of potassium salt and sea salt which provides a 75% reduction in sodium compared to regular table salt. The dietary alternative salt comprises 74.5% potassium chloride and 24.5% sodium chloride and ~1% silicon dioxide (anticaking agent). Intervention participants will receive weekly notifications to their smart phone to remind them to use the SaltSwitch app and dietary alternative salt. Participants will be encouraged to use the dietary alternative salt in place of regular table salt in cooking and at the table, but not to use more or less salt than usual. Delivery of the intervention will be entirely remote with the smartphone app downloaded to participants phones during the randomisation phone call, and the dietary alternative salt being sent by courier to the participant shortly thereafter. Google analytics will be used to monitor use of the SaltSwitch app by individual participants who have WiFii, and the amount of dietary alternative salt left over at the end of the 12-week intervention period will be self-reported in household measures (tsp). Use and acceptibility of the SaltSwitch app and dietary alternative salt will also be self-reported in the follow-up questionnaire.