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Sunday, August 5, 2007 - Page updated at 12:00 AM

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Yours in Health

Green tea and the breast-cancer connection

Special to The Seattle Times

Q: I was reading about green tea being helpful for breast cancer. Is that true? Also, I get insomnia if I have too much caffeine. Is it OK to use decaffeinated green tea, or should I use regular?

A: Green tea has beneficial compounds called polyphenols, or catechins. Most of the research on green tea for breast cancer has been done in Asia because people there drink a lot of green tea.

Green tea may help prevent breast cancer, based on one study in Asian women. Two population studies also found that Asian women with early-stage breast cancer (stages one and two) who drank three to five cups of green tea per day didn't have as many recurrences. The researchers didn't see these benefits for women with later-stage tumors.

The problem, though, is that these are population studies. Remember that this type of research may find associations between green tea and cancer prevention, but it doesn't prove that green tea is the cause for the benefits we are seeing.

On the other hand, there certainly are a lot of good reasons to suspect that green tea might be helpful for cancer. First of all, the polyphenols are great antioxidants. They can protect DNA against things such as free radicals that can damage it and lead to cancer. Also, a specific catechin known as EGCG may prevent new blood vessels from feeding the cancer, and help trigger tumor cells to self-destruct. One study even found that green tea may enhance the effect of a chemotherapy drug, Adriamycin, which is used to treat some types of breast cancer. So far, though, that last experiment has only been done on cells growing in a lab, not in real-life situations.

The amount of caffeine in green tea varies quite a bit, but as a ballpark figure, I usually estimate around 30 mg per cup. By comparison, drip coffee is around 60 to 180 mg per cup. Based on one study done at UCLA, decaffeinated green tea had about half the antioxidant capacity of regular green tea. That said, it may depend on how the tea is decaffeinated. It's thought that a process using carbon dioxide may retain more of the polyphenols and antioxidant capacity than those using ethylene acetate. If you're not sure what process the brand you are drinking uses, you can always call the manufacturer.

Dr. Astrid Pujari is a Seattle M.D. with an additional degree as a medical herbalist; she practices at the Pujari Center and teaches as part of the residency programs at Virginia Mason and Swedish/Cherry Hill hospitals. Send questions to apujari@seattletimes.com for possible use in future columns. All information is intended for education and not a substitute for medical advice. Consult your doctor before following any suggestions given here.

Copyright © 2007 The Seattle Times Company

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