Abstract
Caffeine is one of the most well-known chemical compounds contained in beverages such as coffee, black tea, green tea, and oolong tea. In many cases, these beverages are drunk after being heated. In our previous in vitro studies, it was suggested that such hot caffeine (HC) solution decreased the survival rate of pathogenic bacterial species causing aspiration pneumonia more significantly than in oral bacterial species, and improved the human oral microbiota in a short period of time. For this reason, we performed a single arm, non-blinded intervention test in healthy subjects to reveal the effects of HC on the human oral microbiota. As a result, it was shown that the rate of anaerobic bacteria in the mouth-washing water increased immediately before and after intervention. In this case, the rate of Prevotella was also found to be increasing, suggesting that the increased anaerobic bacteria contained Prevotella. However, a similar increase was not observed in the mouth-washing HC solution. In the HC solution, the number and rate of anaerobic streptococci increased significantly immediately before and after intervention, suggesting that anaerobic bacteria other than Streptococci were decreasing. In contrast, the rates of Fusobacterium and Prevotella in the anaerobic bacteria were found to be increasing. These results suggest that HC caused changes in the human oral microbiota immediately after mouth washing. In addition, the number of aerobic bacteria after mouth washing with HC increased compared with the number before mouth washing in many subjects, suggesting that HC promoted biofilm exfoliation.
