New mechanisms by which black tea could help to prevent cancer have been revealed in two recent studies. Black tea, the most widely consumed beverage in the UK, and its components, has been associated in several in vitro and in vivo studies with the potential to reduce the risk of cancer. As an emerging field of study, it is only very recently beginning to show what the mechanisms for this protective effect might be. These two recently published studies provide intriguing new information in relation to these mechanisms.
Commenting on the studies, Dr Tim Bond of the Tea Advisory Panel notes: "In the first study,1 researchers from New Jersey in the United States evaluated theaflavin-2 (TF-2), a compound unique to black tea (and oolong), which has been shown to kill cancer cells, a process known as apoptosis. This study set out to explore the mechanisms by which theaflavin-2 might induce cancer cell death, including effects on inflammation as inflammation is one contributory mechanism in the development of cancer. This was a laboratory based study that tested cancer cells.
"Theaflavin-2, the component of black tea extract, triggered cancer cell death (apoptosis), inducing shrinkage of cancer cells within 3 hours of treatment. When the researchers looked at a specific set of genes that kill cancer cells, Theaflavin-2 was found to up-regulate or activate these genes. The study also showed the ability of Theaflavin-2 to suppress the activity of a gene that induces the inflammatory enzyme cyclooxygenase (COX) 2 while also reducing the activity of other inflammatory molecules (such as TNF-? and nuclear factor-kappa B (NF-KB). Theaflavin-2 was also shown to reduce inflammation and also produced a pattern of gene regulation similar to that found in the cancer cells. These results suggest that Theaflavin-2, a major component of black tea has the capacity to help kill cancer cells through mechanisms involving gene regulation and an anti-inflammatory effect.
"In the second study,2 researchers from India examined the effect of polyphenols from both black and green tea on the development of breast cancer (mammary tumours) in female rats. Both black and green tea polyphenols significantly reduced the number of mammary tumours by 77% and 92% respectively as well as reducing their growth. When the potential mechanisms for these benefits were investigated, both black and green tea polyphenols were found to scavenge reactive oxygen species by 69% and 72% respectively by inhibiting the inflammatory COX enzyme and inactivating an inflammatory molecule, technically known as NF-KB.
"Taken together, these two studies have demonstrated that components of black tea can help shrink and kill cancer cells and/or result in helping to reduce the number of tumours. These studies indicate that these effects are associated with the ability of black tea components to regulate genes, reduce the activity of COX, an inflammatory enzyme, and reduce the activity of inflammatory substances such as NF-KB."
In summary, Dr Bond adds: "These findings suggest the need for clinical trials to evaluate the effect of black tea and its components on the risk of cancer in humans. In particular, new studies are needed to evaluate the bioavailability of theaflavins and the clinical effects of their metabolic degradation products to shed further light on both mechanisms of action and clinical applications of black tea ingredients. In the meantime, drinking black tea, the UK’s most popular beverage, can continue to be recommended for its many health benefits including the possibility that it could contribute to reducing the risk of cancer."
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