High Potassium Diet Rich in Spices and Herbs-Salt Substitution (HPSH-SS) for Blood Pressure Reduction in Older Adults: Protocol for Diet Concept and Randomized Controlled Trial.

Background: Hypertension increases with age, often due to high sodium (Na) and low potassium (K) intake. Reducing salt and increasing K intake is challenging, especially for older adults due to taste preferences. Culinary herbs and spices, rich in K, offer a potential solution. The High Potassium Diet Rich in Spices and Herbs-Salt Substitution (HPSH-SS) diet has not yet been studied for its effectiveness in lowering blood pressure.

Objective: This study aims to create an HPSH-SS diet, analyze its effects on blood pressure in older adults, and study the molecular mechanism occurring in the kidneys and blood vessels influenced by this diet.

Methods: This study consists of 2 phases. The first phase involved formulating and assessing the HPSH-SS diet tailored for older adults. The intervention group (IG) received a diet of 1800 kcal/day, with 3500 mg K and 1500 mg Na, while the control group (CG) received 1500 mg K and 2000 mg Na. The diet was administered for 14 days and standardized using the NutriSurvey program and biochemistry analysis by atomic absorbance spectrophotometry (AAS). The second phase was a 14-day parallel randomized controlled trial (RCT) with the older adult participants divided into IG and CG. Primary outcomes included blood pressure; serum potassium; aldosterone; F2 isoprostane; nitric oxide plasma levels; and urine analysis of Na, K, and the Na/K ratio. Confounding variables were controlled through randomization and stratified analysis.

Results: The menu formulation and organoleptic assessment of the HPSH-SS diet began in mid-2022 and was approved by the Ethics Committee of the Faculty of Public Health at Universitas Airlangga (78/EA/KEPK/2022) on May 11, 2022. The diet was standardized to achieve daily nutritional values of 1800 kcal energy, 3500 mg K, and 1500 mg Na. K and Na contents were analyzed using AAS from several participants' spice diet menus. Recruitment for the RCT started in March 2023, with approval from the Health Research Ethics Committee Universitas Airlangga School of Medicine, Surabaya (35/EC/KEPK/FKUA/2023). The study was registered from February 9, 2023, to February 9, 2024. Between March and June 2023, 64 participants were recruited, with 32 participants in the IG and CG. The intervention and data collection will take place over 1 year. Data management is in progress, and data analysis is yet to be performed.

Conclusions: This RCT protocol hypothesizes that the diet will increase serum K, plasma aldosterone, and nitric oxide levels; decrease plasma F2 isoprostane; increase urinary Na and K levels; lower the urinary Na/K ratio; and reduce systolic and diastolic blood pressure. If effective, it will offer valuable insights into dietary strategies for blood pressure regulation in older adults.

International Registered Report Identifier (irrid): DERR1-10.2196/56869.