High masticatory ability attenuates psychosocial stress: A cross-sectional study

PLOS ONE RESEARCH ARTICLE High masticatory ability attenuates psychosocial stress: A cross-sectional study Ayako Hashimoto1☯, Aya Nozaki2☯, Hiroko Inoue3, Toshiko Kuwano ID2,4* 1 Department of Food and Nutrition, Faculty of Home Economics, Kyoto Women’s University, Kyoto, Japan, 2 Graduate School of Integrated Pharmaceutical and Nutritional Sciences, University of Shizuoka, Shizuoka, Japan, 3 Department of Nutrition and Health Sciences, Faculty of Food and Nutritional Sciences, Toyo University, Gunma, Japan, 4 School of Food and Nutritional Sciences, University of Shizuoka, Shizuoka, Japan a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Hashimoto A, Nozaki A, Inoue H, Kuwano T (2023) High masticatory ability attenuates psychosocial stress: A cross-sectional study. PLoS ONE 18(1): e0279891. https://doi.org/10.1371/ journal.pone.0279891 Editor: Juan-Luis Castillo-Navarrete, University of Concepcion Faculty of Medicine: Universidad de Concepcion Facultad de Medicina, CHILE Received: August 24, 2022 Accepted: December 16, 2022 Published: January 18, 2023 Copyright: © 2023 Hashimoto et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. ☯ These authors contributed equally to this work. * Abstract Mastication interventions have previously been shown to alleviate acute stress. However, the relationship between masticatory performance and stress response among individuals remains unclear. This study aimed to examine the relationship between masticatory ability and stress response in young women by measuring the autonomic nerve function and salivary α-amylase activity during psychosocial stress. Eighty women (aged 20.0 ± 1.9 years) were divided into either a low or high masticatory performance group, and the Trier Social Stress Test was conducted. Moreover, the autonomic function was measured at rest, immediately before stress, immediately after stress, and 10 min after stress. The salivary α-amylase activity was also measured at rest, 5 min after stress, and 15 min after stress. The visual analog scale (VAS) was used for subjective stress evaluation. There was a significant increase in the autonomic balance of both groups immediately before stress loading, but whilst the high masticatory ability group showed a return to resting-state levels after stress loading, the low masticatory ability group showed elevated levels after stress loading. Salivary α-amylase activity significantly increased 5 min after stress loading in the low, but not high, masticatory ability group. Furthermore, the VAS scores for tension and confusion after stress were significantly higher in the low masticatory ability group than in the high masticatory ability group. Our findings suggest that high masticatory performance may contribute to alleviating psychosocial stress. This is the first study to clarify the relationship between habitual masticatory performance and psychosocial stress suppression in young women. Data Availability Statement: All relevant data are within the paper and its supporting information files. Introduction Funding: TK Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science (KAKENHI, grant number 16K00914). https://www.jsps.go.jp/english/index.html. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Stress is a physiological and psychological response to environmental changes and noxious stimuli that profoundly affect well-being, mood, behavior, and health. The biological response to stress activates the endocrine response of the hypothalamic-pituitary-adrenal (HPA) system and autonomic nervous system response in the hypothalamic-sympathetic-adrenal-medullary (SAM) system [1]. Stress activates the neuroendocrine system via the HPA system, which causes the release of glucocorticoids, including cortisol, which in turn affects various biological PLOS ONE | https://doi.org/10.1371/journal.pone.0279891 January 18, 2023 1 / 13 PLOS ONE Competing interests: The authors have declared that no competing interests exist. High masticatory ability attenuates psychosocial stress functions, such as blood pressure, blood glucose, cardiac contractility, cardiac output, and the immune system [2–4]. Furthermore, when the SAM system is activated, catecholamines are released, resulting in increased blood pressure, sweating, blood glucose levels, and arousal. The stress effects on diseases are supported by experimental findings of animal and human studies showing that the HPA and SAM systems are involved and that various stress stimuli activate these systems. Stress-related illnesses are prevalent worldwide. Stress and coping behaviors have been associated with the development of diseases, including cardiovascular conditions, cancer, breast cancer, colds, and sleep disorders, as well as worsening of symptoms of various disorders, including asthma, irritable bowel syndrome, ulcerative colitis, arthritis, respiratory diseases, skin disorders, and diabetes [2, 5]. Furthermore, stress is associated with symptoms, including headaches, musculoskeletal pain, gastrointestinal upset, hyperventilation, insomnia, fatigue, and depression. Therefore, methods for attenuating stress in daily life should be established to maintain health. Chewing is considered an effective stress coping behavior [2, 6–9]. Mastication affects the activity of the HPA system and autonomic nervous system [2]. Chewing under stress conditions has been suggested to attenuate stress-induced increases in plasma corticosterone and catecholamines [10], and stress-induced changes to the hippocampus and hypothalamus [2]. In rodents, chewing on wooden sticks has been found to increase the expression of carbohydrate corticoid receptors induced by restraint stress and to act as a stress reliever [11]. Chewing under stressful conditions has been found to inhibit stress-induced activation of the autonomic nervous system and localized release of catecholamines at sympathetic nerve endings [12–14]. Furthermore, aggressive biting during stress exposure significantly attenuates the stress-induced increase in dopamine metabolism in hypothalamic and limbic regions, and the noradrenaline metabolic turnover [2, 12, 14]. Numerous human studies have reported the stress-reducing effects of chewing [15–18]. Habitual gum chewing has been found to relieve anxiety and mental stress [16, 19–21]. Gum chewing during stress loading is associated with state anxiety and decreased salivary cortisol levels [18]; additionally, chewing and light teeth clenching after stress loading rapidly decreases salivary cortisol levels [22]. Notably, a fast masticatory speed and strong masticatory force cause a greater reduction in mental stres (...truncated)