Effects of Yoghurt on the Human Oral Microbiota and Halitosis

Objective: Many investigators have studied the preventive effects of yoghurt on gastrointestinal infection and malfunction. Moreover, it was reported that the regular consumption of yoghurt reduced the caries risk. The purpose of this study was to investigate the effects of non-sugar-type traditional yoghurt fermented by Streptococcus thermophilus and Lactobacillus bulgaricus on the human oral microbiota and halitosis. Method: We recruited twenty-four volunteers who gave their informed consent to participate in the present study program. The Ethical Committee of Tsurumi University approved the study protocol. Two weeks before the start of the study, each volunteer received identical instructions for the oral hygiene, diet and medicine intake. During non-intake phase, the volunteers were asked to consume neither yoghurt nor the products containing streptococci and lactobacilli such as cheese and pickled vegetables. During yoghurt intake phase, the volunteers consumed 90g of yoghurt twice daily for 6 weeks. We analyzed a microbiota of samples collected from saliva and tongue coating. The volatile sulfide compounds (VSC) concentrations in the mouth air were measured using portable gas chromatography. Results: VSC levels, namely hydrogen sulfide, in 80% of volunteers who had oral malodor decreased at 6 weeks. As compared to the non-intake phase, the numbers of fusobacteria in tongue coating also were reduced by eating yoghurt (p=0.08). There were no noteworthy differences in the number of oral bacteria, such as black-pigmented anaerobic rod, lactobacilli, and mutans streptococci. The salivary pH shifted more neutrally from 7.27 in non-intake phase to 7.05 in yoghurt intake phase (p<0.01). The plaque and gingival index of the yoghurt intake phase was significantly (p<0.05) lower than those of the non-intake phase among the volunteers who had oral malodor. Conclusion: The results suggest that traditional yoghurt intake may reduce the components of oral malodor and harmful bacteria.