# Measurement of sodium in soft tissue and bone in a sodium diet intervention study using in vivo neutron activation analysis

## TL;DR

This study uses neutron activation analysis to measure sodium in human soft tissue and bone after dietary changes, showing how sodium levels respond to low and high sodium diets.

## Contribution

The study introduces in vivo neutron activation analysis for measuring sodium in soft tissue and bone in response to dietary interventions in humans.

## Key findings

- Soft tissue sodium decreased in half of participants on a low sodium diet, with reductions ranging from 8% to 55%.
- All participants on a high sodium diet had elevated soft tissue sodium compared to those on a low sodium diet.
- Bone sodium levels remained stable regardless of dietary intervention, ranging from 1000–2000 ppm.

## Abstract

Sodium (Na) overconsumption has been associated with hypertension risk and progression. Human soft tissue and bone are recognized as quickly and slowly exchangeable compartments for sodium storage. How such a distribution regulates blood pressure remains unknown. This study performed in vivo Na measurements on human subjects who underwent dietary intervention, utilizing a compact neutron generator-based neutron activation analysis system. It aimed to evaluate the performance of this innovative system for body Na assessment.

Participants were provided with low and high sodium diets. Baseline measurements were taken before each intervention feeding period, and follow-up measurements were conducted afterwards. The human hands were irradiated for 20 min, followed by 2 cycles of Na gamma ray collection. A biokinetic model was used to calculate sodium concentrations in soft tissue and bone, reflecting sodium accumulation in the two compartments.

For soft tissue, Na levels after low Na diet decreased from baseline in half of the subjects, with reductions ranging from 8% to 55%. The other half of participants exhibited relatively stable Na content. Among participants consuming high Na diet, all participants had elevated Na in soft tissue compared to those on low Na diet. By contrast, Na in bone showed no significant changes from baseline and follow-up for either dietary intervention. Bone Na concentrations ranged from approximately 1000–2000 ppm.

For the first time, Na in soft tissue and bone was measured in humans using neutron activation analysis in response to dietary interventions. This study demonstrates that in vivo neutron activation analysis can be used to measure Na concentration in both soft tissue and bone. It successfully detects Na alteration in soft tissue and explores the biokinetics of Na retention following dietary interventions. Measuring soft tissue and bone sodium content is a potentially useful approach to study diet and disease links affected by sodium.