Many studies have implied that the regular consumption of black tea can protect against a range of human cancers. Now scientists think they know why, ReutersHealth reports. Black tea's 'secret weapon' may be a compound called theaflavin-3'-monogallate (TF-2), one of a family of potent anti-cancer compounds called polyphenols. TF-2 "shows very interesting properties''against colon cancer cells, according to researcher Dr. Kuang Yu Chen of Rutgers University in New Brunswick, New Jersey. Speaking on Wednesday at the annual meeting of the American Chemical Society, Chen explained that while exposure to TF-2 leaves normal cells unharmed, cancer cells ''commit suicide'' in droves. In laboratory experiments, Chen's team added tea-derived TF-2 to both healthy cells and colorectal cancer cells. Normal cells flourished, the researchers report, while malignant cells underwent a process called apoptosis - programmed cell death. Investigating further, the Rutgers team discovered that TF-2 appears to suppress the activity of the Cox 2 gene. This gene has been the focus of intense scientific research because, when 'switched on,' Cox 2 helps triggers the inflammation process, an integral part of the sequence of events that can cause normal cells to turn into cancer cells. "The relationbetween Cox 2 and colon cancer has been very well established,'' Chen said. Many questions remain to be answered, however. Scientists have not yet determined the optimum level of black tea consumption needed before any significant anti-cancer benefit kicks in. And Chen stressed that his findings regarding TF-2 remain preliminary, requiring further study in animal and human models. Polyphenols are found in other foods and drink, including green tea and grape skins, but polyphenols in both those foods exhibit a ``less dramatic'' effect against cancer cells, according to the researchers.