Abstract / Summary
Hydrogen gas may improve autonomic regulation. The effects of hydrogen-rich jelly (HRJ) on autonomic responses during postural transition have not yet been investigated. This double-blind, randomized, placebo-controlled crossover trial evaluated HRJ effects on heart rate variability (HRV) in 50 healthy adults (21 men; mean age, 44.2 ± 11.3 years). HRJ (30-40 ppm, 10 g) or placebo was orally administered 24 h, 1.5 h, and immediately before testing. HRV was recorded during an orthostatic loading protocol with four 1 min phases: seated rest, stand-up, standing, and resitting. Among the 48 participants with complete data, no significant difference in the primary endpoint of high-frequency was observed. Exploratory analyses revealed lower coefficient of variation of the R-R interval (CVRR) during the stand-up phase (mean difference: -0.46, p = 0.047) and lower low-frequency-to-high-frequency (L/H) ratio during the resitting phase (mean difference: -1.51, p = 0.027), with no significant differences at rest or during standing. Subgroup analyses suggested stronger responses in women and those with lower skeletal muscle mass (CVRR), and in younger participants, those with higher body mass index, and habitual alcohol consumption (L/H). HRJ may induce mild, stage-specific changes in HRV during postural transitions. However, their physiological and clinical significance remains uncertain and should be clarified in future studies.