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Randomized Controlled Trial
. 2024 Jan 13;14(1):1261.
doi: 10.1038/s41598-024-51851-9.

Evaluation of the benefits of neutral bicarbonate ionized water baths in an open-label, randomized, crossover trial

Ryoko Ushikoshi-Nakayama  1 , Tomoe Yamazaki  1 , Daisuke Omagari  1 , Naoyuki Matsumoto  1 , Hiroko Inoue  2 , Chiyoko Nukuzuma  3 , Seiji Nishino  4 , Ichiro Saito  5   6
Affiliations
Randomized Controlled Trial

Evaluation of the benefits of neutral bicarbonate ionized water baths in an open-label, randomized, crossover trial

Ryoko Ushikoshi-Nakayama et al. Sci Rep. .

Abstract

We previously demonstrated that neutral bicarbonate ionized water (NBIW) bathing enhances blood flow by bicarbonate ions and described the underlying mechanism. However, additional clinical investigation was warranted to investigate the efficacy of NBIW bathing. Hence, we performed a randomized, open-label, crossover trial to examine the effects of 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; sleep quality, with the Pittsburgh Sleep Quality Index Japanese version (PSQI-J) 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 naive to memory T cell ratio and neutrophil phagocytosis, indicating improved immune function. These findings suggest that daily NBIW bathing could improve mental stress, sleep quality, and immune function and bring about positive health effects in those who experience stress in their daily lives.

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Conflict of interest statement

IS a representative director of Cranescience Co., Ltd., Tokyo, Japan, and receives compensation and stock ownership. The other authors declare no competing interests.

Figures

Figure 1
Figure 1
Flow diagram of the randomized crossover-controlled trial. NBIW, neutral bicarbonate ionized water.
Figure 2
Figure 2
Assessment of stress with the Brief Job Stress Questionnaire. The Brief Job Stress Questionnaire (BJSQ), simplified version for primary outcome of mental stress, consists of 23 questions and was scored separately for the 3 stress categories. The graph shows the rate of change in scores from baseline (minus SD) on the vertical axis. A: control, − 13.92 (− 14.13); NBIW, − 16.32 (− 11.92). B: control, − 18.96 (− 17.03); NBIW, − 24.08 (− 10.53). C: control, − 4.14 (− 11.25); NBIW − 11.11 (− 15.08). N = 50 (control, n = 25; NBIW, n = 25). *p < 0.05 tested by paired t test. #: Parameters with significant changes from baseline (p < 0.05; tested by Wilcoxon rank sum test). NBIW, neutral bicarbonate ionized water.
Figure 3
Figure 3
Test for carryover effect. For the percentage change from baseline in the Brief Job Stress Questionnaire-Social Support (BJSQ-C), the intervention periods were grouped into NBIW and control and compared with a t test. The first and second periods of the control intervention showed no significant difference (p = 0.308), and the same was found for the first and second periods of the NBIW intervention (p = 0.335). Thus, no carryover effect was observed.
Figure 4
Figure 4
Sleep quality assessment with the Japanese version of the Pittsburgh Sleep Quality Index. The primary outcome sleep quality was assessed by the Japanese version of the Pittsburgh Sleep Quality Index. The graph shows the percentage change in scores from baseline (minus SD) on the vertical axis. Control, − 25.67% (SD, − 27.67%); neutral bicarbonate ionized water, − 37.08% (SD, − 26.33%). *p < 0.05 tested by paired t test. NBIW, neutral bicarbonate ionized water.
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