An 88-patient parallel RCT tested NamakBan, an Android app enabling self-reported salt intake logging, blood pressure tracking, and medication recording, against standard care alone in Iranian adults with diagnosed primary hypertension. Over two months, the app group achieved statistically significant greater reductions in both systolic and diastolic blood pressure, alongside larger declines in self-reported daily sodium intake. Crucially, the objective biomarker — urinary sodium-to-potassium ratio — did not differ significantly between groups, and hospitalization differences were non-significant.
The disconnect between subjective and objective sodium measures is the critical finding here. When self-reported dietary data improves but urinary Na⁺/K⁺ ratio — a well-validated, hard-to-fake physiological marker — does not budge, social desirability bias becomes the most plausible explanation. Participants who know they are being monitored may report eating less salt without meaningfully changing behaviour, a Hawthorne effect amplified by unblinded self-reporting. The blood pressure reductions, while real, may reflect increased medication adherence (the app also logged drugs) or heightened health awareness rather than sodium reduction per se.
This is a small, single-centre, short-duration trial with Android-only reach, limiting generalisability. Digital health interventions for hypertension are a legitimate and growing field, but the bar for credibility should be objective biomarker improvement. Until studies with longer follow-up confirm urinary sodium changes, NamakBan's blood pressure benefits remain mechanistically unresolved. Incremental finding, not practice-changing.