Can Green Tea Help People With Breast Cancer?
Key Takeaways:
Some studies in people suggest that drinking green tea may slightly reduce the risk of breast cancer and cancer from coming back.
Drinking green tea may lower breast density.
Drinking green tea is safe for most people, but always check with your doctor.
There hasn’t been much research in people taking green tea supplements.
Besides being a warm and tasty drink, green tea can also be good for you. More studies are needed, but some research suggests that when drunk regularly, green tea may help lower the risk of cancer. It can also improve heart health and help with weight loss.
The components of green tea that give it most of its health benefits are antioxidants called catechins. Antioxidants help protect cells from oxidative stress, a type of damage that can increase the risk of many diseases like cancer, heart disease, and diabetes. There are several types of catechins. The one that shows the most promise is called EGCG.
What the research shows
Green tea can’t cure cancer, but it may reduce the risk of some cancers, including breast cancer. It may also lower the risk of breast cancer coming back (recurrence). Most research in people is based on drinking green tea, but studies in animals and cells often use green tea extract or EGCG.
Cancer risk
Drinking green tea may lower the risk of some cancers, including non-Hodgkin’s lymphoma and endometrial, lung, oral, and ovarian cancer, according to a review study. (A review study provides an overview of existing studies on the topic.) It’s less clear if green tea might reduce the risk of breast cancer. Some studies found that it does, while others found that it doesn’t. Overall, the review found that drinking green tea is linked to a 15% lower risk of breast cancer. Other review studies have found similar results. But researchers say they can’t be sure with the evidence they have so far, so more studies are needed.
Recurrence risk
There haven’t been many studies on whether green tea affects the risk of breast cancer coming back. But the few studies that did look at this suggest drinking green tea may also lower recurrence risk. For example, one study found that drinking green tea lowers the risk of recurrence by 19%. Another review found that drinking green tea before being diagnosed with stage I and II breast cancer is linked to a 44% lower risk of recurrence. But more studies are needed to understand the link between green tea and breast cancer recurrence.
Breast density
One way that green tea may lower breast cancer risk is by reducing breast density. People with dense breasts are more likely to develop breast cancer. One study found that women aged 45 to 74 who drank green tea daily had lower breast density than women who didn’t drink green tea. Another study found that post-menopausal women aged 50 to 55 who took green tea extract for one year had reduced breast density, but older women did not.
Cancer treatment side effects
Applying green tea supplements to the skin may ease side effects of radiation therapy. Two small studies in people with breast cancer found that spraying the skin with a liquid EGCG supplement reduced skin pain, burning, itching and tenderness from radiation.
Cells and animal studies
Studies in cells and animals are an important early step in research. But you can’t draw conclusions about how things will work in people based on these studies. For example, treating cells with green tea extract in a lab dish won’t tell researchers how green tea is absorbed and broken down by the human body when someone drinks it. And breast cancer in a mouse may or may not behave like breast cancer in a person. These studies are still important, though, as they can help researchers find leads to explore in people.
Cell and animal studies have found that green tea extract may boost the effects of tamoxifen by killing more cancer cells, slowing tumor growth, and lowering levels of estrogen receptors in tumors. EGCG may boost the effects of chemotherapy, and another study found that it may reduce chemotherapy side effects like gastrointestinal problems and organ damage.
Other studies in cells show that catechins may be able to prevent metastasis and the growth of blood vessels that feed tumors. But the body isn’t good at absorbing catechins from green tea and getting them into cells — including tumor cells, where they need to be to fight cancer. So although cell studies are promising, green tea and its components aren’t as effective as they could be at fighting cancer in people. Researchers are trying to develop ways to help catechins get into cells better, but this is a work in progress.
Other uses
Early research suggests that green tea, its extract, and EGCG can benefit many areas of health. The best evidence for green tea health benefits other than cancer are for weight loss and heart health.
Weight loss
A recent review study found a weak link between drinking green tea and weight loss. In other words, green tea may help you lose weight, but not by a lot.
Heart health
The same review study found that drinking green tea is linked to a lower risk of heart issues, including stroke, high blood pressure, and death from heart disease. Drinking green tea also lowers the risk of heart attack.
Safety, risks, and side effects
Green tea is generally safe, and many people drink it every day. But it’s not clear how much green tea you have to drink to see health benefits, or if green tea extract or EGCG supplements have the same effects.
Some studies suggest benefits at three or more cups of green tea per day. Others have found benefits at four, five, or even 10 cups per day. If you want to take a green tea supplement, it’s also not clear how much you should take. Some experts recommend a maximum of 600 mg of EGCG per day, while others recommend up to 800 mg or 1,000 mg. Always check with your doctor before starting a new supplement.
Green tea contains caffeine that can keep you up at night and cause headaches. (Decaffeinated green tea has less catechins, so it may be less helpful for fighting cancer.) In rare cases, high doses of green tea can damage the liver. Drinking hot tea may raise the risk of esophageal cancer, so let it cool a bit before drinking.
Side effects of green tea may include nausea and stomach pain. Do not drink green tea if you have a stomach ulcer. Limit caffeine from green tea and other sources to 200 mg per day if you are pregnant or nursing; this is equal to about four to seven cups of green tea, depending on the variety. Be cautious of green tea if you are taking an iron supplement because green tea can change how the body absorbs iron.
So should you drink more green tea?
Drinking green tea and taking green tea supplements won’t cure cancer, but drinking green tea is generally safe and can be used as a complementary therapy. Studies in people suggest that green tea lowers breast cancer risk and the risk of recurrence, but more research is needed. Talk to your doctor before taking green tea as a supplement.