The Benefits of Neutral Bicarbonate Ionized Water Baths: An Open-Label, Randomized, Crossover Trial

We performed a randomized, open-label, crossover trial to examine the effects of neutral bicarbonate ionized water (NBIW) bathing on mental stress, sleep, and immune function. Participants who regularly felt stressed were randomly assigned to NBIW or regular bathing for 4 weeks. Mental stress was assessed with the Brief Job Stress Questionnaire (BJSQ) and the Profile of Mood States Second Edition (Japanese version); sleep quality, with the Pittsburgh Sleep Quality Index (PSQI-J; Japanese version) and actigraphy; and immune function, with laboratory tests. PSQI-J scores and actigraphy sleep latency and bed out latency improved significantly more with NBIW bathing than with regular bathing ( p < 0.05). Furthermore, NBIW bathing reduced both stress-induced fluctuations in CD4 + and CD8 + T-cell counts and fluctuations in the naïve to memory T cell ratio and neutrophil phagocytosis, indicating improved immune function. These findings suggest that NBIW bathing improves mental stress, sleep quality, and immune function.