A study published in the Journal of Environmental Pathology, Toxicology and Oncology revealed that chemicals in black tea called polyphenols reverse cancer-causing changes to the DNA of cells lining the mouth, reported science portal Scidev.

Researchers at the Vivekanada Institute of Medical Sciences in Kolkata, monitored white patches called 'leukoplakia' in the mouths of patients drinking black tea three times a day for one year.

The preliminary study conducted over 15 patients saw a remarkable change in those white patches due to the intake of black tea. Even some patches disappeared completely.
 
Generally half of the white patches in the mouth lead to oral cancer.

Although the findings relate to a small number of patients, lead researcher Ajanta Haldar said: "The patches also disappeared in a further seven patients who have completed the trial since publication of the initial results."

Sixty more patients are being studied and will complete the trial by April 2006.

The study funded by National Tea Research Foundation of India will further assess whether the white patches reappear in patients who have completed the yearlong trial and then ceased drinking black tea for six months.
 
In 2002, oral cancer claimed 145,500 lives, two-thirds of which were in developing countries. It is the most common form of malignant cancer found in adult Indian men and the third most common in adult Indian women.

Earlier scientists at the Memorial Sloan-Kettering Cancer Centre in the US also found that polyphenol in green tea could slow the growth of pre-cancerous mouth cells.

Researchers of the current study claimed that they are the first to show a similar effect with black tea.

Another ongoing research by Madhumita Roy of Kolkata's Chittaranjan National Cancer Institute shows that black tea combined with anti-cancer drugs can force cultured human leukaemia cells to commit suicide.

"This makes tea an ideal candidate to reduce the dose of anti-cancer drugs by almost ten times, overcoming the toxic side effects of high drug dose," Roy said.