Effects of Chewing Frequency on Cerebral Blood Flow and Cognitive Function

The purpose of the present study was to examine the effect of the frequency of mastication on cerebral activation and task scores for computational tasks. Eleven healthy subjects participated in the present study (nine women, two men). Subjects carried out the Uchida-Kraepelin Test for 15 min before and after chewing tasteless gum for five minutes. The oxygenation of the left prefrontal cortex was monitored by near-infrared spectroscopy during the computational tasks. Task scores did not differ significantly according to chewing frequency (p > 0.05). Conversely, the oxygenation value measured after mastication at a chewing frequency of 110 times/minute (Hz) was significantly higher than that observed before mastication (p < 0.05). Meanwhile, before and after levels of oxygenation did not differ significantly for chewing frequencies of 30 Hz and 70 Hz (p > 0.05 for both). The results of the present study suggest that tasteless mastication does not enhance calculation performance, while a high mastication frequency demonstrates an influence on oxygenation. However, our study indicates that chewing tasteless gum per se does not increase cognitive performance.

Weight Perception and Diet Behavior of Japanese and Russian Adolescent Girls

Niigata City in Japan and Khabarovsk City in Russia signed a sister city agreement in 1965 and have been interacting with each other for a long time. We have been conducting comparative research on the elderly between the two cities, but there is no research on the young. Distorted perception of body weight and unnecessary dieting behavior in adolescent girls is considered a problem in both Japan and Russia. Therefore, the purpose of this study was to clarify the distortion of weight perception and diet behavior of adolescent girls in both the countries. In addition, it was decided to investigate the eating habits of people in both the countries. In total, 195 15-year-old girls from Niigata, Japan (October 2020) and 286 girls from Khabarovsk, Russia (February 2017) were surveyed. The questionnaire used was an excerpt from the World Health Organization survey on the health behavior of school-age children. The proportion of Japanese adolescent girls who perceived themselves as overweight (distorted body weight perception) was 60.5%, which was significantly higher than that of Russian adolescent girls at 30.1% (p < 0.001). In addition, the prevalence of weight loss behavior in Japan was 34.9% (n = 68), which was significantly higher than that in Russia with 27.3% (n = 78) (p < 0.001). Adolescent girls in Japan had more serious problems with weight perception, but had fewer problems with breakfast and vegetable intake habits than those in Russia. From a young age, perception of correct body shape and establishment of eating habits are important not only for current health but also for future health. We need to carefully educate adolescent girls that their body undergoes major changes through secondary sexual characteristics during adulthood.

Eating with Familiar Friends Decreases the Electrical Taste Threshold

Communal eating reportedly induces changes in food-related behaviors such as increased consumption and alleviation of indefinite complaints. Here, we examined the influence of intimacy with co-eaters on the palatability of the food and the physiological taste thresholds. The study was a single-blind crossover trial with 16 healthy women aged 18 - 19 years (two close friends × 8) as participants. We examined the effect of four preset conditions with regard to taste (condition 1 = tasting alone;condition 2 = tasting with a friend;condition 3 = tasting with three unfamiliar individuals;condition 4 = tasting with a friend and two unfamiliar individuals). Electrical taste thresholds were measured pre-and post-eating. The subjective evaluation of taste did not show any significant difference between the four conditions (p > 0.05). However, the electrical taste threshold significantly decreased when eating with close friends (p < 0.05). As a factor associated with the meal environment, co-eating with family or friends appears to influence tastiness;however, in the present study, it showed no effect on the perception of taste. Nevertheless, eating with friends significantly decreased the electrical taste threshold and enhanced the perception of taste. Decrease in the electrical taste threshold was observed only when eating with a close friend;it was not observed when eating with other people and showed no association with the total number of individuals co-eating.

Relationship between the Influence of Others’ Opinions on Taste during Co-Eating and the Empathy of Individuals

The purpose of this study was to investigate whether the opinions of people eating together affect the taste of the foods they eat. In addition, if the opinions of others influence taste for one of the people eating with them, are the others’ opinions related to the empathy of individuals? Finally, this study was also intended to consider whether the taste threshold changes depending on the opinions of others. Twelve healthy young women (aged 18.4 ± 0.8 years;mean ± SD) participated in the present study. The participants tasted bread under three conditions: 1) quiet condition: a participant ate with three quiet persons, 2) positive condition: a participant ate with three persons who were talking favorably about taste, and 3) negative condition: a participant ate with three persons who were talking negatively about the taste. The electrical taste threshold was tested before and after tasting the bread, and a visual analog scale (VAS) was completed immediately after the tasting. Before the first trial, participants were asked to complete the Interpersonal Reactive Index (IRI). In the positive condition, the taste score increased significantly compared with the negative condition. There was no significant relationship between taste and empathic concern. To our knowledge, taste changed according to the comments of other people who were eating together. However, the change in taste due to the other’s speech was not related to the individual’s empathy. The results of the present study suggest that people experience food as delicious when others eating with them comment about the food being “delicious,” and this tendency did not depend on individuals’ empathy.