Does Green Tea have a Dark Side?
In my book, Naturally Supporting Cancer Treatment, I talk about the benefits of drinking green tea for cancer prevention and those studies are definitely valid. However, there is some evidence to show that it can have some negative effects.
The most worrying research shows that in large doses green tea can increase the effects of 5-fluorouracil (5-FU) significantly. 5-FU is a chemo drug that is used to treat a wide variety of cancers. So it’s important to keep your intake to less than 6 cups per day, which is considered safe. The cups used, though, are the small ones that you find in Chinese restaurants, which only hold about 100 mls of liquid. So we’re talking less than 600 mls per day, which equates to about 2 mugs full (1).
There is also evidence that green tea can inhibit the effects of bortezomib, which is used to treat myeloma and glioblastoma (2). If you’re being treated with bortezomib, don’t drink green tea or take green tea supplements.
A single study indicates that green tea inhibits a certain enzyme that processes vemurafenib (3), which is used to treat malignant melanoma. So it may increase the levels of the drug, which could be dangerous.
Green tea interacts with nadolol, a drug that is used to control high blood pressure. If you drink green tea for more than 2 weeks it reduces nadolol’s levels by 85% (2).
Don’t be tempted to use green tea extracts, which are widely used to help lose weight. They have been shown to reduce the absorption of plant-derived iron significantly and also to reduce the levels of iron in the blood (4). Taking green tea extracts in large doses, that is over 800 mg of EGCG daily, over a long period can also reduce the absorption of folate supplements unless they’re taken with food, which reduces the effect.4 Those sort of doses over 4 months or more will also raise the levels of your liver enzymes, which is very unwise if you’re having chemo treatment (5).
Isn’t it interesting that something that we would all consider to be a normal thing to consume can have such effects? It just goes to show the effects of food and drink can have on our bodies and how they react to other chemicals.
