Does Green Tea Help Prevent or Treat Breast Cancer?

Epigallocatechin-3-Gallate (EGCG) and Breast Cancer

Green tea may help prevent and treat breast cancer
Green tea has many health benefits, including protection against breast cancer. Nick Purser/Getty Images

Could green tea play a role in preventing—or even treating—breast cancer? There's been a lot of talk about the benefits of drinking green tea in recent years. Among the headlines are several claims that a chemical found in the beverage may be a powerful weapon against breast cancer. But before you load up on green tea bags and start chugging away, you should learn a bit more about this alleged miracle brew and the science behind it.

Green tea is made from the leaves of the Camellia sinesis, a plant native to parts of Asia. It has been a popular drink in that part of the world for many years and is gaining popularity here in the West. It was actually the low rate of breast cancer (and some other cancers) in regions where people drink large amounts of green tea which made researchers question the role of the tea in cancer prevention.

Antioxidants and Free Radicals

Green tea's cancer-fighting reputation comes from its polyphenols, chemicals that have antioxidant properties (among others). Antioxidants protect the cells in your body from free radicals, highly reactive molecules that speed the damage caused by chemicals in the environment or aging, and which can lead to the development of cancer.

Free radicals can damage tissues in many ways, including directly damaging DNA. Since it is damage to DNA—gene mutations—which leads to the development of cancer, there has been great interest in nutrients which can neutralize these free radicals before they do their damage.

One of the antioxidants found almost exclusively in green tea is epigallocatechin-3-gallate (EGCG), which has been at the heart of recent green tea headlines. Other examples of antioxidants include lycopene, found in cooked tomatoes, and vitamin A, found in carrots.

Since we are talking about 2 different scenarios—those who are hoping to do anything possible to prevent themselves from developing breast cancer, and those who want to do everything possible to treat their breast cancer—we will break this down into these separate areas.

Green Tea and Breast Cancer Prevention

Many studies have looked at the role of green tea and breast cancer prevention. These include studies that have look at green tea from the standpoint of knowing it is an antioxidant, as well as studies based on a lower incidence of breast cancer in areas in which green tea consumption is common. Not all studies have found an association between green tea drinking and lower breast cancer risk, but some of the largest, most credible studies do find an association.

In the Prostate, Lung, Colorectal, and Ovarian Screening Trial, a study which looked at over 100,000 people, it was found that those who consumed green tea had a lower overall risk of cancer—in other words, it appeared to reduce the risk of any cancer in the study. The good news didn't stop there, however, and there's more. Whereas some studies have looked at very large amounts of green tea—say, drinking 30 cups daily—this study looked at people who drank one cup of green tea daily. That's pretty doable for most of us.

A 2017 study looked at mammographic density in women given a supplement of EGCG for 1 year. While breast density did not change for older women, it significantly decreased in young women, similar to the effect of tamoxifen (which is sometimes used to reduce the risk of breast cancer in high-risk individuals) The researchers concluded that further studies should be done on the the role of green tea in reducing breast cancer risk in young women.

Green Tea and Breast Cancer Treatment

Could drinking green tea help for those who already have breast cancer? In other words, could it slow down an existing disease process? So far most studies have been done on breast cancer cells in the lab, or in mice, but the results to date are encouraging. After all, if you're living with breast cancer you realize that the majority of treatments come with significant side effects. Wouldn't it be nice to have something that not only has few side effects, but is aesthetically pleasing to boot? (In these studies green tea is not used as a substitute for conventional treatment, but rather as an adjunct to the best current treatment approaches.)

The news on the treatment side is good as well, with some researchers suggesting that green tea may one day become part of a breast cancer treatment plan. To understand the growth of cancer, and how green tea may work, it's helpful to think of the different processes  that must take place for cancer to grow and spread. In looking at these separate steps in growth researchers have found:

  • That green tea appears to inhibit the growth of cancer. Several studies have found the division of breast cancer cells and increase in size of a tumor (albeit in a lab dish or in mice) was decreased by green tea components.
  • Green tea was found in a few studies to inhibit the spread—metastasis—of breast cancer cells. Since most people die from cancer metastases rather than the primary cancerous tumor itself, this is very good news. Green tea given to rodents with breast cancer was found to limit metastases to the lungs and liver, common places for breast cancer to spread.
  • That green tea may help with programmed cell death—apoptosis—of breast cancer cells. To understand this it helps to understand that normal cells "commit" apoptosis when they become injured or old. Cancer cells seem to have found a way to avoid this process, making them "immortal" in a way.

Effect of Green Tea on Breast Cancer Treatments

It's important to talk to your doctor about your diet and especially any nutritional supplements or vitamins you wish to use during cancer treatment. Some vitamin or mineral supplements may interfere with treatment, and this is true with dietary supplements as well. This is easier to understand if you consider the purpose of treatments such as chemotherapy and radiation therapy. These treatments are designed to kill cancer cells. It would be counterproductive to use a supplement which "protected" cancer cells. That said, some phytochemicals appear to have a protective effect on normal cells but not cancer cells.

Of importance to many people being treated for breast cancer is the possible effect on long term treatment—hormonal therapy—for breast cancer. The news on this account looks good. It was found in a few studies that green tea acted together with Tamoxifen and Raloxifene in a positive way. In other words, the combination of green tea and one of these medications worked better for inhibiting estrogen positive breast cancer cells than either the medication, or green tea, alone. The other medication people with breast cancer often use long term is one of the aromatase inhibitors such as Aromasin. Studies suggest that green tea does not interfere with the function of this medication.

Thankfully, studies looking at both estrogen receptor positive and estrogen receptor negative breast cancer cells found some possible benefits from green tea.

Tips for Enjoying Green Tea

As its popularity grows in the Western world, green tea is getting easier to find; if it's not on the shelf at your local supermarket, check with a nearby health food store or Asian market. Green tea does contain caffeine, although there are caffeine-free varieties available. Be on the lookout for potential side effects, such as heart palpitations and nervousness, and adjust consumption as needed. Learn how to brew green tea for health benefits as the method of brewing the tea can make a difference in the amount of EGCG absorbed.

If you usually add creamer to your green tea, you may want to stop. Dairy products contain compounds that bind EGCG and inhibit absorption. In contrast, adding a touch of lemon appears to result in better absorption (and hence effectiveness) of EGCG in green tea.

Finally, you'll need something to eat with your tea. A handful of walnuts may help fight breast cancer, and omega-3 in fish may help prevent breast cancer. And don't forget to stock up on cruciferous vegetables, which are crammed with anti-cancer power.

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