title: Influence of chewing rate on salivary stress hormone levels.
abstract: OBJECTIVE
  The purpose of this study was to clarify the effect of different chewing rates on salivary cortisol levels as a stress indicator.
  
  
  METHODS
  The subject group consisted of 16 healthy males. They were required to rest for 30 min, and then given arithmetic calculations to perform for 30 min as stress loading. Immediately after, the first set of saliva specimens (S1) was collected over a period of 1 min to measure cortisol levels. Next, they were asked to chew a tasteless gum base for 10 min, and the second set of saliva specimens (S2) was collected in the same manner. They were then required to rest for 10 min, after which the third set of saliva specimens (S3) was collected. Chewing rates were set to slow, habitual, and fast in time with a metronome. Salivary cortisol levels were analyzed by radioimmunoassay. Changes in salivary cortisol levels comparing S1 with S2, and S1 with S3 were determined.
  
  
  RESULTS
  Changes in salivary cortisol levels between S1 and S2 showed a reduction of 4.7%, 14.6%, and 16.2% with slow, habitual, and fast chewing, respectively. A significant difference was observed between slow and fast chewing. Changes in salivary cortisol levels between S1 and S3 showed a reduction of 14.4%, 22.2%, and 25.8% with slow, habitual, and fast chewing, respectively. A significant difference was observed between slow and fast chewing.
  
  
  CONCLUSIONS
  This study showed that differences in chewing rate affected salivary cortisol levels as a stress indicator, and suggested that the effect on stress release with fast chewing is greater than that with slow chewing.
authors.affiliation: Department of Removable Prosthodontics and Gerodontology, Tokyo Dental College, Chiba, Japan. atasaka@tdc.ac.jp
authors.forename: Akinori
authors.initials: A
authors.lastname: Tasaka
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Tahara
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Sugiyama
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sakurai
mesh_terms: D000328:Adult; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D008297:Male; D008409:Mastication / Q000502:physiology*; D012463:Saliva / Q000737:chemistry*; D013315:Stress, Psychological / Q000378:metabolism
chemical_list: D006854:Hydrocortisone