An excellent study (published in October 2010, in Breast Cancer Research) reported that consumption of green tea provides no benefit in reducing the risk of developing breast cancer. The authors examined the prospectively collected data on 53,793 women, in Japan, who provided information on their level of consumption of green tea over a 5-year study period. They looked at various factors to determine if there were any subcategories of women who might have experienced a reduced risk of of developing breast cancer, but they could not find any correlations (i.e. demographics, amount of green tea consumed, type of tea consumption, hormone receptor status, etc.)
Although this very well conducted study did not demonstrate any benefit in consuming green tea in reducing the risk of developing breast cancer, this study does not answer some critical questions (for example):
- Does green tea slow cancer progression? (Their are clinical and preclinical studies that suggest it may.)
- Does green tea decrease the carcinogenic impact of various environmental or behavioral risk factors? (i.e. smokers who drink green tea may have a significantly lower risk of developing lung cancer)
- Does green tea increase/decrease the percentage of developing more/less aggressive tumors (i.e. histology, tumor grade, tumor stage at presentation, etc.) ?
- Does extracted EGCG (the most potent antioxidant and antiangiogenic inhibitor phytonutrient component of green tea) have significant anti-cancer benefits?
There is no doubt that some hardcore green tea ‘believers’ will argue with the conclusions of this study. At this time, I would say that this is as good of a study as we are going to get for a long while, and I feel that the results are likely real. If there is a breast cancer prevention benefit from consuming green tea, it is probably quite small.
The jury is still out on the questions I pose, above. These are important issues to address, as they may have significant implications (i.e. if green tea consumption decreases the incidence of more aggressive or higher stage tumors, then drinking green tea will clearly be of benefit, etc.) Furthermore, green tea consumption may exert significant anti-cancer benefits after a diagnosis of breast cancer. Additional studies will need to be conducted to examine this potential benefit.
In the meantime, enjoy the relaxing (or energizing effects, as green tea has caffeine) benefits of green tea.