A compound in green tea called EGCg inhibits the activity of an enzyme required for cancer cell growth, according to a study recently released in the United States.
The study confirms previous studies which showed that people who drink four or more cups of green tea daily run a lower-than-average
risk of cancer. What has not been clear in past studies however is why? While scientists had speculated that EGCg (short for epigallocatchin gallate) might be at least partially responsible, this is the first study to demonstrate this.
The scientists who conducted the study, led by Dr James Morre of Purdue University in West Lafayette, Indiana, reported their findings at the annual meeting for the American Society of Cell Biology in San Francisco, California. The Morre team found that green tea inhibited the activity of an enzyme called tumour-associated quinoloxidase, or tNOX, an overactive form of an enzyme known as NOX.
The NOX enzyme is found on the surface of cells and plays a key role in growth of both normal and cancerous cells. Normal cells produce the NOX enzyme only when hormonal signals prompt the cells to divide. But cancerous cells appear to be able to produce the abnormal form, tNOX, all the time. The tNOX protein has been found on many types of cancer cells, including breast, prostate and colon cancer cells. Drugs that inhibit tNOX have been shown to block cancer cell growth in the laboratory.
Black or ordinary tea made from one part tea leaves to 10 parts water inhibited tNOX activity, the researchers found. But green tea inhibited the activity more, when diluted 10 to 100 times. Both black and green tea comes from the same plant, but black tea leaves are processed differently.
