Do you have bad breath, really bad breath?
It might not be the garlic or onions, coffee or alcohol.
Rather, a new study links it to the types of bacteria that dominate the back portion of the top of your tongue.
Some bacteria protect against halitosis, the formal name for really bad breath, while others cause the pungent odor, says a team of researchers from The Forsyth Institute in Boston and the University of Michigan School of Dentistry.
"I think there's a definite smoking gun here -- that it's a strong association," says lead researcher Bruce Paster, a senior staff member at Forsyth. "There are the good bacteria and the bad ones. Normal bacteria keep out bacteria from the bad guys."
The study, reported in the February issue of the Journal of Clinical Microbiology, relied on gene sequencing to compare bacteria found on the tongues of those with halitosis and those with fresh breath.
Researchers reported species of the same three bacteria were prevalent among five people with fresh breath. The most common of these germs found on these subjects' tongues, Streptococcus salivarius, appeared in only one of six people with halitosis -- and at extremely low levels.
About 65 million Americans suffer from halitosis at some point in their lives, the National Institute of Dental Research has estimated. Halitosis differs from the temporary mouth odors caused by foods or drinks.
Six species of bacteria were linked to halitosis, and several of those germs were not found in those with fresh breath.
The study is part of an ongoing effort to determine genetic sequences for all species of bacteria in the oral cavity. Paster says that the results have been confirmed by still-unreported research involving a larger group of people and adds that forthcoming research will look into possible treatment for halitosis.
Differences in bacteria in people's mouths -- and, in turn, why stinky sulphurous bacteria is so prevalent in halitosis sufferers -- could be the result of a variety of factors, including blood type, Paster says.
"I think it's a case where it's clear that with these people who have halitosis, something makes these types of bacteria more likely to colonize than ones that colonize normal tongues," he says.
However, uncovering all the bugs responsible for good and bad breath could be a daunting task.
About 75 to 100 different kinds of germs live in each person's mouth -- of a total of 700 that collectively populate all human mouths, Paster says. Of these, scientists know the names of only about 300.
You have more bacteria in your mouth than cells in your body, says Paster, and a toothpick plaque sample would hold 10 million to 100 million cells.
The researchers reported finding just 92 species of bacteria, 29 of which had never before been described in scientific literature. So other bugs could be responsible for good breath and bad, Paster says.
He suggests you could help reduce halitosis by brushing not only the teeth, but also the tongue, twice daily, along with scraping the tongue and using oral care products containing zinc.
Dr. Israel Kleinberg, chairman of the oral biology and pathology department at the State University of New York at Stony Brook's dental school, says the study shows how different bacteria in the mouth help determine whether bugs conducive to good or bad breath thrive.
He likened these variations to differences in climates where different types of vegetation grow. "There are environmental differences that can be selective" in the mouth, too, Israel says. "It's the environment that ends up selecting the bacteria. So if you want to do something about it, you want to try to shift that environment."
And what of mouthwashes that promise to kill bacteria that cause bad breath?
"You can try to kill bacteria, but by and large, the bacteria grow back," Kleinberg says. "Most of the effort is toward killing bacteria, and killing bacteria is not terribly effective in most cases."