Subgroup differences in calcium metabolism in response to dietary sodium: Rationale, design, and methods of a randomized, controlled, crossover dietary intervention in healthy adults.

The growing interest in personalized nutrition stems from a deeper understanding of subgroup differences in response to environmental factors, including diet. Preliminary evidence in Black and White adolescent girls showed that Black girls retain more calcium and excrete more sodium compared to White girls on a high sodium diet. However, little is known about calcium absorption efficiency across other races or age groups. This report outlines the rationale and design of a planned randomized controlled trial aimed at investigating calcium absorption and calcium and sodium excretion in response to diets high (typical Western diet) and low (recommended) in sodium in Black, White, Hispanic, and Asian adults. It is hypothesized that fractional calcium absorption and urinary sodium excretion will vary by subgroup, with Blacks predicted to have the highest rates and Whites the lowest, and intermediate responses in Hispanics and Asians. Participants will undergo two 2-day dietary intervention arms, with biospecimen collection following each arm. Primary outcomes include fractional calcium absorption and urinary calcium excretion, and secondary outcomes comprise urinary sodium excretion and blood pressure. Findings from this study could advance precision nutrition by informing strategies to alleviate osteoporosis and cardiovascular diseases risks across different race/ethnicity groups.