Dietary approach to stop hypertension (DASH) diet reduces blood pressure (BP) as effectively as one antihypertensive drug, yet its mechanism of action was never fully characterized.

We designed a translational inpatient trial to elucidate the biological pathway leading from nutritional change, through hormonal response, reversal of urine electrolytes ratio, to BP reduction.

A single-center open-label interventional trial. Volunteers were admitted for 14 days, transitioning from an American-style diet to DASH diet. Vital signs, blood, and urine samples were collected daily. Participants completed two 24-hour ambulatory BP measurements (ABPM) and two 24-hour urine collections on days 1 and 10. Nine volunteers completed the protocol. During inpatient stay, serum aldosterone increased from day 0 (mean 8.3 ± 5.0) to day 5 (mean 17.8 ± 5.8) after intervention and decreased on day 11 (mean 11.5 ± 4.7) despite continuous exposure to the same diet (p-value = 0.002). Urine electrolyte ratio ([Na]/[K]) decreased significantly from a mean of 3.5 to 1.16 on day 4 (p < 0.001). BP by 24-hour ABPM decreased by a mean of 3.7 mmHg systolic BP and 2.3 mmHg diastolic BP from day 1 to 10.

Shifting from a high-sodium/low-potassium diet to the opposite composition leads to aldosterone increase and paradoxical BP reduction. Urine electrolyte ratio reflects nutritional changes and should guide clinicians in assessing adherence to lifestyle modification.