In the East Asian cultural sphere, moxibustion has long been established as a traditional thermal therapy with a rich history spanning thousands of years, during which it has been widely integrated into daily healthcare practice. In recent years, modern molecular biological findings have begun to unveil its scientific basis, revealing the crucial involvement of transient receptor potential (TRP) channels—specifically thermo-TRP channels—in mediating cellular responses to such thermal stimulation. Building upon these cellular-level discoveries, several physiological studies have successfully reported the diverse systemic effects of moxibustion-like stimulation, particularly its regulatory impacts on central brain function and the enhancement of local muscular blood flow [1][2]. Furthermore, ongoing research has been actively elucidating its complex mechanism of action on the autonomic nervous system by utilizing heart rate variability (HRV) as a non-invasive, quantitative index of sympathetic and parasympathetic activity [3][4].

Clinically, moxibustion applied to specific acupoints on the lower limbs, most notably SP4 (Sanyinjiao), has been documented to elevate skin temperature not only locally but also remotely in the lateral and abdominal regions, thereby effectively mitigating menstrual pain and related discomforts [5]. Thus, it has been empirically and observationally recognized since ancient times that pedal stimulation contributes significantly to the regulation and homeostasis of the digestive system. However, despite its widespread utilization and perceived efficacy in modern clinical settings, the rigorous accumulation of robust scientific evidence and its underlying multisystemic mechanisms remain insufficient. Therefore, to bridge this gap between traditional empirical knowledge and modern science, this study aims to comprehensively elucidate the physiological and psychological impacts of pedal moxibustion on the abdominal region. To achieve this, we employ a multifaceted approach that incorporates objective peripheral body temperature measurements, validated psychological testing via the State-Trait Anxiety Inventory (STAI), and an exploratory analysis of the gut microbiota.

It is suggested that Yojo (health cultivation) practices in traditional medicine potentially influence host homeostasis through alterations in the gut microbiota and the gut-brain axis.

First, regarding the relationship between axillary body temperature elevation and the gut microbiota, Takeda et al. reported that an increase in body temperature during hot spring bathing leads to a significant increase in Bifidobacterium bifidum [8]. Although a tendency toward hypothermia is generally noted in patients with chronic diseases, including cancer [9][10], our intervention revealed an increase in the relative abundance of the genus Faecalibacterium accompanying a trend toward elevated body temperature. Although this change did not reach statistical significance, these findings suggest a potential link between thermogenesis (body temperature elevation) and the proliferation of specific beneficial bacteria.

Second, a key characteristic of many traditional medical interventions is their direct or indirect action on the gastrointestinal tract. For instance, many Kampo medicines are administered as decoctions; they exert their pharmacological effects by passing through the intestinal tract, which houses approximately 70% of the body’s immune cells and harbors a vast microbiota. Furthermore, regarding moxibustion—a therapy involving thermal and physical stimulation of the body surface—the acupoint Zusanli (ST36), frequently used to promote health, is known to activate gastrointestinal motility via the autonomic nervous system. In recent years, there has been a rise in research aimed at elucidating the mechanisms of traditional medicine from the perspectives of the immune system and gut microbiota. Yamashita et al. demonstrated that the tumor cell growth-inhibitory effect of Inchinkoto depends on the composition of the gut microbiota [11], while Shi et al. reported immunological effects of Daikenchuto administration, such as the activation of group 3 innate lymphoid cells (ILC3) and the amelioration of experimental colitis [12]. These findings suggest that traditional medical interventions have the potential to boost immunity through the intestinal tract.

Third, physical symptoms associated with vague complaints—such as sensitivity to cold, chronic lower back pain, and menstrual pain—often stem from psychosocial stress or negative emotions manifesting as abnormal peripheral sensations [13]. Recent research on the “brain-gut axis” suggests that functional changes in the serotonin (5-HT) system within the insular cortex are involved in these seemingly localized physical sensations [14]. The gastrointestinal tract, which produces approximately 90% of peripheral serotonin, is also a primary site where the gut microbiota modulates the immune system [15]. This implies that traditional medical therapies (such as moxibustion) may influence the close interrelationship between central emotional and cognitive networks by acting through the gut environment.

Based on this background, we hypothesized that a health-promoting practice (moxibustion) might alter the gut microbiota in a manner beneficial to the host by raising body temperature. To test this hypothesis, we conducted a multifaceted analysis incorporating body temperature measurements, psychological indicators, and gut microbiota profiling.

This study employed a single-group, pre-post intervention design without a control group. Consequently, changes in the gut microbiota or symptoms cannot be definitively attributed to the moxibustion treatment. Furthermore, the findings are merely the results of exploratory, intra-individual observations.

This study has several limitations. First, the sample size was limited to ten female participants, and the study was conducted exclusively during the month of December. Second, the moxibustion treatment was self-administered at home, meaning the results may have been influenced by confounding variables, such as variations in dietary and lifestyle habits. Third, while the State-Trait Anxiety Inventory (STAI) was utilized to measure anxiety, it is necessary to consider the potential impact of anxiety specifically related to the moxibustion procedure itself among participants who were novel to the practice.

Nevertheless, it is noteworthy that changes in gut microbiota profiles were observed in all participants following the intervention. Future verification of this hypothesis will require larger-scale studies involving an increased number of participants and a control group, while strictly controlling for confounding factors such as dietary intake and lifestyle habits.

This study was supported by The Uchida Energy Science Promotion Foundation (Grant Number R8-1067) and the Japan Society for the Promotion of Science’s Grants-in-Aid for Scientific Research (Kakenhi Grant No. 26K13356).

The authors thank the volunteers who participated in this study. We thank Dr. Keita Kamezaki (Metagen, Inc., Yamagata, Japan) for analysis of gut microbiota.

Conceptualization, M.W., K.O., T.M., T.Y., N.M. and C.T.; methodology, T.N. and M.R.; formal analysis, M.W., K.O., T.M. and N.M.; investigation, M.W., K.O. T.M., T.Y. and T.K.; data curation, M.W., K.O. T.M., T.Y. and T.K.; writing—original draft preparation, M.W., K.O. T.M., T.Y. and T.K.; writing—review and editing, T.N., M.R., T.N., N.M., C.T. and T.T.; visualization, X.X.; supervision, M.W.; project administration, M.W.; funding acquisition, M.W. All authors have read and agreed to the published version of the manuscript.