The preliminary results of a study at the Vivekananda Institute of Medical Sciences in Kolkata, published in the Journal of Environmental Pathology, Toxicology and Oncology, show that micronuclei frequency and chromosomal aberrations significantly decreased in the first 15 participants to complete a year-long program of drinking black tea (Camellia sinensis) three times a day.
Although the positive results relate to just a small group, they are consistent across all subjects who have completed the study so far. The results for another 67 participants will be available by April 2006. Micronuclei are fragments of chromosome that are not incorporated into the nucleus at cell division, indicating the inability of cells to repair damaged DNA. Tests for their presence are used as a diagnostic for cancer risk.
Changes in the appearance and quantity of leukoplakia white spots in the mouths of the patients who have completed the study to date were also noted.
According to the Vivekananda Institute researchers, oral carcinoma is the most common malignancy found in Indian men and the third most common in Indian women. In half of all cases, precancerous lesions, usually leukoplakia, appear prior to the development of full-blown cancer.
Most of the research into tea's potential for reducing the risk of various types of cancer has involved green tea which, although also derived from Camellia sinensis), contains different active compounds to black tea due to its production process.
For green tea the leaves are steamed and dried, a procedure that preserves catechin polyphenols such as the powerful antioxidant epigallocatechin gallate (EGCg).
Black tea, on the other hand, is made by oxidizing the leaves, which converts the EGCg into other compounds. In the past scientists have unfavorably compared the benefits of compounds such as theaflavins and thearubigens to EGCg, but black tea is starting to gaining credence as a health-promoting preparation in its own right.
The researchers carrying out the latest study drew attention to a 1998 study at Memorial Sloan-Kettering Cancer Center in the United States, which showed that green tea could slow the growth of precancerous mouth cells.
"To the best of our knowledge, this is the first report on the effect of black tea in oral leukoplakia," they wrote.