Drinking black tea 'reduces risk of mouth cancer'
[KOLKATA] Drinking black tea could help prevent oral cancer, say researchers at the Vivekanada Institute of Medical Sciences in Kolkata, India.
They monitored white patches called 'leukoplakia' in the mouths of patients drinking black tea three times a day for one year.
"About half of the white patches in the mouth ultimately lead to oral cancer," says co-author Madhusnata De.
In the first 15 patients to complete the trial, the precancerous patches disappeared completely.
India's National Tea Research Foundation funded the study, whose initial results were published in the latest issue of the Journal of Environmental Pathology, Toxicology and Oncology.
Although the findings relate to a small number of patients, lead researcher Ajanta Haldar says 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.
Haldar believes that chemicals in black tea called polyphenols reverse cancer-causing changes to the DNA of cells lining the mouth.
The next phase of the study will assess whether the white patches reappear in patients who have completed the year-long trial and then ceased drinking black tea for six months, says Haldar.
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.
In 1998, researchers at the Memorial Sloan-Kettering Cancer Centre, United States, showed that a polyphenol in green tea could slow the growth of precancerous mouth cells. Halder's team says it is the first to show a similar effect with black tea.
Both black and green teas are produced from Camellia sinesis. Green tea is prepared from the steamed and dried leaves of the shrub. Black tea is produced by withering, rolling, fermenting, and then drying the leaves.
As a result of the different processes, the teas contain different compounds.
The anti-cancer properties of green tea are well documented, but some researchers believe black tea has them too.
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 says.
"An extract of about 11 grams of tea — either green or black — per day may reduce risk of stomach, colon, liver, lung and skin cancers," agrees Ashok Giri of Kolkata's Indian Institute of Chemical Biology, whose research on this was published in Mutation Research in 2002.
In comparison, patients in Haldar's trial consumed about eight grams of black tea every day.
Link to abstract of paper by Halder et al
Reference: Journal of Environmental Pathology, Toxicology and Oncology 24, 103