Dr Paul Clayton 2010
There is already a good deal of work that indicates that tea – both green and black – has anti-cancer effects. This was recently reinforced by a joint American/South Korean study, led by the US Department of Agriculture, and published in the Journal of Agricultural and Food Chemistry (Friedman et al ’06).
Many of tea’s health benefits, including cancer protection and a reduced risk of Alzheimer’s, have been linked to the flavonoids found in tea. Green tea contains 30 to 40 per cent of flavonoids, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent. But tea contains other good things too, including compounds called theaflavins, and the unusual amino acid l-theanine.
The researchers looked at the effects of each of these in isolation, and then at the effects of a whole tea extract (which is what we drink) against a range of common cancer cell lines. These included breast, lung, prostate and colon cancer cell cultures; and in each case, the tea extracts killed large numbers of the cancer cells, with higher concentrations of tea killing larger numbers than weaker extracts. “These findings extend related observations on the anti-carcinogenic potential ingredients of tea, and suggest that consumers may benefit more by drinking both green and black teas,” wrote lead author Mendel Friedman from the USDA.
Other scientists have shown that the tea polyphenols can reduce the formation of certain carcinogens (d’Ischia et al ’06), but it is becoming abundantly clear that these valuable compounds can directly arrest and kill many cancer cells, and force others to re-differentiate; an important process that effectively renders them harmless.
These and other studies have led key researchers at the University of Leicester to recommend large-scale clinical trials of the tea flavonoids in the prevention of prostate and cervical cancers (Thomasset et al ’07). Given that tea is pretty safe – especially when compared to the highly toxic anticancer drugs currently used – I wholeheartedly agree with them. I would also point out that most soft drinks, unless made with fruit juice, contain none of the anti-cancer compounds outlined above.
Friedman M, Mackey BE, Kim H-J, Lee I-S, Lee K-R, Lee S-U, Kozukue E, Kozukue N. Structure – Activity Relationships of Tea Compounds against Human Cancer Cells. J Agric Food Chem Published on-line ahead of print ASAP Article doi: 10.1021/jf062276h S0021-8561(06)02276-X.
d’Ischia M, Panzella L, Manini P, Napolitano A. The chemical basis of the anti-nitrosating action of polyphenolic cancer chemopreventive agents. Curr Med Chem. 2006 13(26):3133-44.
Thomasset SC, Berry DP, Garcea G, Marczylo T, Steward WP, Gescher AJ. Dietary polyphenolic phytochemicals promising cancer chemopreventive agents in humans? A review of their clinical properties. Int J Cancer. 2007 Feb 1 120(3):451-8.