Salt Sensitivity Evaluation Via N-of-1 Trials (SENSE-Salt)

Study Title: Determining the Presence of Salt Sensitivity in Individuals With Elevated Blood Pressure Through Dietary Salt Interventions: A Series of N-of-1 Trials

Objective: To evaluate whether there are differences in blood pressure responses to dietary sodium intake between salt-sensitive and salt-resistant individuals, as identified through a salt sensitivity test. The study will use repeated dietary interventions with varying sodium content (high-sodium, low-sodium) to assess blood pressure responses in each individual, aiming to determine whether salt sensitivity is a present characteristic.

Study Design: This study will utilize an N-of-1 randomized controlled trial design. It consists of two phases:

Salt Sensitivity Screening: A 2-week chronic salt-loading test will be used to identify salt-sensitive and salt-resistant individuals.

N-of-1 Trial: The identified salt-sensitive and salt-resistant individuals will undergo a 6-week N-of-1 trial, consisting of three cycles, with each cycle including one week of low-sodium diet and one week of high-sodium diet. This design aims to assess individual blood pressure responses to changes in sodium intake.

Sample Size: A total of 72 participants will be recruited for the salt sensitivity screening, with an expected 24 participants proceeding to the N-of-1 trial.

Study Population: Healthy individuals aged 20-65 years, not on antihypertensive medication or with a stable regimen for at least 3 months, with systolic blood pressure between 110-159 mmHg and diastolic blood pressure between 70-99 mmHg, who are able to eat at the research center.

Primary Outcome: Reproducibility of salt sensitivity response classification. Secondary Outcomes: Changes in mean arterial pressure, systolic and diastolic blood pressure; exploratory outcomes such as sleep, mood, gut microbiome, metabolomics; safety outcomes including hypotension and hyponatremia.