A salt-logging app lowered blood pressure in two months. The urine tests hint salt may not be the whole reason

Cutting salt is one of the first things people with high blood pressure are told to do, and one of the hardest to keep track of. In much of the world the salt comes mostly from packaged food, but in Iran the largest share is the salt people add themselves while cooking and at the table. A team at Shahid Beheshti University of Medical Sciences built a Persian-language Android app, NamakBan, aimed at that home-added salt, and tested it in a randomised trial published in Nursing Open on 6 October 2026.

The trial enrolled 88 adults with primary high blood pressure from a specialist clinic at Shahid Modarres Hospital in Tehran between April 2024 and September 2025. Half had usual clinic care, which already included spoken and written advice on diet, medicines and measuring blood pressure at home. The other half had the same care plus the app, in which they logged blood pressure readings (shown green or orange), the salt they used in teaspoons or grams with a conversion table, and their medicines with reminders, and could print a PDF summary for the clinic. Everyone was followed for two months and nobody dropped out.

Blood pressure fell in the app group, from an average of 133/84 to 126/78 mmHg, while the usual-care group barely moved (131/82 to 130/81). At two months the app group was 4.45 mmHg lower for the top number and 2.94 mmHg lower for the bottom one. Reported salt use dropped from 6.6 to 4.9 g a day with the app, just under the World Health Organization's limit of 5 g, against 7.0 to 6.6 g a day with usual care. But the one objective check, the sodium-to-potassium ratio in a urine sample, fell by about the same amount in both groups (1.39 to 0.99 with the app, 1.40 to 1.01 without), so it did not confirm the gap in salt.

The authors themselves call the salt result the weakest finding. People in the app group knew they were being tracked and logged their salt every day, and self-reported salt is known to be under-reported. They also work out that the reported cut, about 1.7 g of salt a day, would explain only part of the blood pressure difference, and suggest that regular home readings with feedback and medicine reminders may account for the rest, though the trial could not separate them. Four people on usual care were admitted to hospital for high blood pressure and none with the app, a difference that could be chance. The trial was small, single-centre, Android-only and short; the app was built by the research team, and only the statistician was blinded. They call for a larger trial lasting at least a year with 24-hour urine tests.