In a small study, Japanese researchers found that eating traditional, sugarless yogurt reduces the compounds that cause bad breath It also cuts down on the amount of plaque and gingivitis, they say.
Lead author Kenichi Hojo and colleagues from Tsurumi University in Yokohama, Japan, decided to investigate yogurt because of its success in preventing gastrointestinal problems and research indicating that regular yogurt consumption reduces the risk of dental decay.
"We were thinking that yogurt must be good for oral health also," says study co-author Nobuko Maeda, a professor of microbiology at the University.
The researchers recruited 24 volunteers, each of whom received identical instructions for oral hygiene, diet and medication.
In the initial phase of the study, participants were asked not to consume yogurt or products containing streptococci and lactobacilli, such as cheese and pickled vegetables. During the second phase, they ate 90 grams (a little more than 3 ounces) of yogurt, twice a day for six weeks.
The yogurt they consumed was made especially for the study, which was funded, in part, by a major Japanese yogurt maker. This yogurt contained a different strain of bacteria than is usually used in other yogurts, Maeda says.
Halitosis, or bad breath, is caused by anaerobic bacteria that breed on the back of the tongue and produce volatile sulfur compounds. So, researchers collected samples from the participants' saliva and tongue coatings, and measured the concentrations of these compounds on the participants' breaths.
At the end of the study, those measures showed that levels of one sulfur compound decreased in 80% of the volunteers who had bad breath at the start of the study.
In addition, plaque and gingivitis were significantly reduced after the yogurt-intake phase of the study, compared with the initial phase when they did not consume yogurt.
However, the authors say there were no noteworthy differences in the amount of oral bacteria in the mouths of people before and after eating yogurt, as might have been expected.
But Bruce J. Paster, senior staff member in the department of molecular genetics at The Forsythe Institute in Boston, says, "Their hypotheses may (still) be valid."
He theorizes there may be the same amount of bacteria because the odor-causing species may have been replaced by some 'good' species in the yogurt."