Natural chemicals found in black tea, called polyphenols, help fight the bacteria that cause bad breath, say researchers at the University of Illinois at Chicago. Bad breath, also known as halitosis, is caused by volatile sulphur compounds produced by bacteria that thrive in oxygen-lacking environments, such as the back of the tongue and deep gum pockets. In the laboratory, polyphenols not only inhibited the growth of oral bacteria, they also suppressed by 30 percent the enzyme that catalyzes hydrogen sulfide, a halitosis culprit. The study corroborates earlier evidence that black tea suppresses dental plaque and tooth decay. While black tea has the highest halitosis-fighting properties, green tea also contains polyphenols.