W A S H I N G T O N, May 22, 2001 -- You won't find it served at your dentist's office just yet, but drinking black tea between meals may help reduce cavities and plaque, researchers said on Tuesday.
New studies, funded by the Tea Trade Health Research Association, found several doses of black tea every day not only reduced plaque build-up but also helped control bacteria.
"We found that the black tea infusion can inhibit or suppress the growth of bacteria that promotes cavities and affect their ability to attach to tooth surfaces," Christine Wu, professor of periodontics at the University of Illinois and lead researcher on one part of the study.
Wu said that while earlier studies in Japan have shown the cavity-fighting benefits of green tea, known for its rich antioxidants, her team chose to focus on black tea, which is more popular in western culture.
The research is part of a collaborative study done in conjunction with the College of Dentistry at the University of Iowa and the Institute of Odontology at Goeteborg University in Sweden. The findings were presented at a meeting of the American Society for Microbiology in Orlando, Florida.
300 Species of Bacteria
Dental plaque contains more than 300 species of bacteria that adhere to tooth surfaces and produce cavity-causing acid. Plaque is also a leading cause of gum disease.
A specific element of black tea, called polyphenols, killed or suppressed cavity-causing bacteria from either growing or producing acid, according to Wu's study. The tea also affected the bacterial enzymes and prevented the formation of the sticky-like material that binds plaque to teeth.
Participants in the study rinsed with tea for 30 seconds, five times, waiting three minutes between each rinse.
"We were trying to simulate what people did while sipping tea," Wu said.
A similar study by Goeteborg University, where participants rinsed with tea for one minute 10 times per day, showed comparable results. Both studies showed that the more people rinsed, the more their plaque and bacteria levels fell.
In the University of Iowa study, researchers looked at the impact of black tea's fluoride content on preventing cavities but found the benefits less clear. They exposed pre-cavity lesions to black tea but saw little change, suggesting that tea's cavity-fighting ability stems from a complicated reaction between it and bacteria.
Fluoride Not A Factor?
"We had very little results, which implies that if tea is having a result in normal use it's not from fluoride," said James Wefel, professor and director of the Dows Institute of Dental Research at the University of Iowa.
Of course, to help prevent cavities the tea must truly be "black," without sugar, milk, honey or other additives. Researchers also stressed drinking black tea should not replace traditional oral hygiene.
"Tea will affect the plaque formation but one has to brush their teeth to remove the plaque," Wu said. "It's a must." And while black tea may fight cavities, it does not combat tooth stains.
"It is going to stain (people's) teeth, but at least we know it's good for oral health," Wu said.