Christine Wu and Min Zhu of the University of Illinois at Chicago College of Dentistry isolated chemical components of tea leaves known as polyphenols and tested them against three species of bacteria known to cause bad breath. The researchers found that the compounds, specifically catechins and theaflavins, inhibited growth of the oral bacteria over a 48-hour incubation period. What is more, lower concentrations of the chemicals interfered with the enzyme that catalyzes the production of hydrogen sulfide, which has the notorious smell of rotten eggs, and reduced its production by 30 percent. The compounds studied by the scientists are present in both green tea and black tea, although they are more abundant in the latter.
In a second study, researchers reported that green tea may provide additional benefits. Milton Schiffenbauer of Pace University and his colleagues tested tea's ability to fight bacteria that cause infections such as strep throat and dental caries. They found that green tea extracts and polyphenols--particularly those from caffeinated beverages--inhibited bacterial growth. Adding these agents to toothpaste and mouthwash, he notes, may make them more effective at combating microbial agents.