Cinnamon Cleans the Breath

People plagued by halitosis—bad breath—may have a friend in cinnamon. Dental scientists in Chicago have shown that an essential oil from this spice can kill oral bacteria, including germs responsible for a chemical that imparts the rotten-egg smell to the breath. But one doesn’t have to suck on a cinnamon stick to knock out the offending microbes. Chewing a stick of gum will do.

Wm. Wrigley Jr. Co.

Min Zhu and her coworkers at the University of Illinois at Chicago College of Dentistry had been looking in mints and other common plants for essential oils that kill oral germs. Although many extracts showed promise, few proved as potent as oily cinnamic aldehyde, the principle flavor compound in cinnamon.

Although common experience indicated that chewing gum might make the breath smell better, the prevailing suspicion had been that simply the act of chewing anything—even unflavored wax—would stimulate saliva production that would “flush away, like a river, much of the bacteria in your mouth,” notes Christine D. Wu, associate dean of the dental school. Suspecting there was more to it, she persuaded the Chicago-based Wrigley Co. to finance a study of its top-selling cinnamon gum, Big Red.

Zhu’s team recruited 15 people to come in for a trio of tests, each 3 days apart. They arrived with teeth unbrushed—and most with fetid breath. The first thing each person did was drool into a cup.

The researchers then tallied the number of bacteria per unit volume in each volunteer’s saliva, including both benign bacteria and germs that can spawn bad breath. The latter tend to come from the back of the mouth, Wu explains. Unlike the cavity-fostering bacteria that produce plaque, bad-breath germs don’t eat sugars. Instead, they chow down on proteins. One by-product of that bacterial meal is smelly hydrogen sulfide. As creatures that can’t survive in the presence of much oxygen, these microbes hide out in pockets at the back of the tongue or in the gums.

After the study participants drooled in the name of science, it was chew time. On each test day, the recruits received a stick of gum to chomp on for 20 minutes. One time it was the cinnamon gum. Another time, it was a special formulation made with all of the gum’s flavorings except cinnamic aldehyde. The third version was the totally unflavored base used to make Wrigley gums.

Twenty minutes after each volunteer had discarded his or her gum, the recruit produced some more saliva for analysis. If chewing was all it took to wash away bacteria, the unflavored gum should have reduced oral-bacteria counts about as well as the others.

But it didn’t, Zhu, Wu, and their colleagues reported in Honolulu 2 months ago at a meeting of the International Association for Dental Research. The unflavored gum didn’t affect bacterial numbers at all. By contrast, the fully flavored cinnamon gum killed half of all oral bacteria and 40 percent of the types linked to bad breath. Among those were such species as Porphyromonas gingivalis, Fusobacterium nucleatum, Prevotella intermedia, and Peptostreptococcus micros.

The big surprise, Wu told Science News Online, was that the middle formulation—the gum with some flavorings but no cinnamon oil—performed nearly as well at knocking out the oral bacteria as did the regular gum. The researchers had expected gum without cinnamic aldehyde to be an inert product when it came to germ killing, Wu says.

Subsequent consultation with Wrigley’s chemists turned up a different plant extract in the gum’s recipe that explains the bactericidal action, Wu says. However, Wrigley hasn’t yet given her permission to disclose what this secret flavoring is.

What she’d like to do now is pit a plain gum flavored solely with cinnamic aldehyde against the Big Red recipe minus that essential oil to see which is the more potent at quashing bacteria. If they’re equally effective, Wu says, it will indicate that there exists some maximum antibacterial impact for gums containing the usual ingredients.

Wu says her group’s findings can’t necessarily be extrapolated to other cinnamon-flavored gums, since their recipes may include other ingredients that may either diminish or enhance the cinnamon oil’s antibacterial action.

Don’t like gum? The findings suggest there may be other dietary approaches to vanquishing foul-smelling oral germs. Consider spiced teas. Three years ago, Wu reported that rinsing teeth several times a day with black tea—a test meant to simulate the action of drinking the brew—inhibited the growth of the germs that lead to cavities (Science News Online, Food for Thought: 7/14/01; A Brew for Teeth—and the Rest of You). Because some commercial black teas are flavored with cinnamon, they might do double duty—killing germs responsible for both caries and halitosis. With luck, Wu says, she’ll turn up the money to investigate that.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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