In previous blogs, I have reported on the apparent health-benefits of green tea, and in particular its apparent association with a reduced risk of cancer. This beverage is rich in phytochemicals (naturally-occurring plant substances) known as polyphenols that have what is known as ‘antioxidant’ activity. This means that they have the potential to quell disease-promoting molecules known as free radicals in the body.
In a recent study published on-line in the journal Carcinogenesis, the association between green tea drinking and breast cancer was assessed . In this study, green tea drinkers, compared to non-drinkers, tended to be different for other reasons including a tendency to consume more fruits and vegetables (probably protective for breast cancer) and alcohol (which probably increases cancer risk). In this study, these and other factors (known as ‘confounding factors’) were taken account of in an attempt to make as accurate an assessment as possible regarding the actual association between green tea drinking and breast cancer.
This study found that women consuming 750 grams or more of green tea leaves each year were at a 39 per cent reduced risk of breast cancer compared to non-drinkers. Each cup of green tea is generally made with a teaspoon (about 2.5 grams) of leaves. 750 grams of dried leaves per day equates to only 300 cups of green tea over the course of a year: less than one each day.
So-called ‘epidemiological’ studies of this sort can never be used to ‘prove’ that green tea protects against breast cancer.
However, the fact that this study took account of common confounding factors strengthens its findings. Also, green tea is known to contain substances that one would expect might help to protect the body from cancer. One particular polyphenol offered by green tea that has attracted particular attention is known as epigallocatechin gallate (EGCG). EGCG has been found to have a number of cancer-protective actions in the body, including an ability to help in the deactivation of cancer-causing chemicals (carcinogens).
Take all of this into consideration, as well as previous research linking green tea with cancer protection, and there seems to be pretty good reason to think that green tea has potential benefits in this respect.
1. Zhang M, et al. Green tea and the prevention of breast cancer: a case-control study in southeast China. Carcinogenesis. 2006 December 20 [Epub ahead of print]