Green Tea: The Attack on Cancer

Green tea contains numerous polyphenols (antioxidants), called catechins. One of these catechins, called epigallocatechin-3-galate or EGCG, is one of the most powerful nutrients against mechanisms that cancer cells need to invade tissues and create new blood vessels.

Introduction

Research in recent years has shown that the polyphenols (antioxidants) in green tea have an inhibitory effect on the occurrence and growth of cancer.

How does it work?

When you drink green tea, you ingest the cathechin EGCG. EGCG then spreads through your bloodstream throughout your body. EGCG settles through the small capillaries on the surface of the cells and attaches to the receptors that are responsible for delivering the signal that causes cancer cells to invade the tissue. EGCG can also block receptors that want to create new blood vessels. This creation of new blood vessels are orders from the cancer cells that want to create new blood vessels to enable the growth of tumors. By blocking this, the tumor cells do not receive enough nutrients to grow into a large tumor. Research has shown that EGCG significantly slows the growth of leukemia cells, breast cancer cells, prostate, kidney, skin and oral cancer cells.

Green tea and cancer

Breast cancer

Clinical studies in animals and in test tubes suggest that polyphenols in green tea inhibit the growth of breast cancer cells. One study of 472 women with various stages of breast cancer found that women who drank the most green tea had the least spread of cancer. This was especially the case in premenopausal women in the early stages of breast cancer. This study found that women who drank at least five cups of green tea a day in these early stages of the disease, before they were diagnosed with cancer, were less likely to have the cancer return after they finished treatment. However, women in later stages of breast cancer showed little to no improvement from drinking green tea. In a very large study, researchers found that drinking tea, green or other types, was not associated with a reduced risk of breast cancer. However, when the researchers changed the sample and divided the study by age, they found that women under the age of fifty who consumed three or more cups of tea per day were 37% less likely to develop breast cancer compared to women who didn’t drink tea.

Research showed:

  • EGCG can work well with other anti-cancer agents. For example, EGCG appeared to significantly improve the effect of the anti-estrogen Tamoxifen (commonly used in breast cancer) and hormone-insensitive tumor cells also responded to Tamoxifen through EGCG.
  • Also, together with resveratrol (from red wine) and a vitamin E component, EGCG showed a lower dose and better effectiveness of chemotherapy in breast cancer cells.
  • In animal research and in cell cultures with human breast cancer cells, a stabilized form of EGCG (pro-EGCG) appeared to be considerably more effective than EGCG.

Ovarian cancer

In a clinical study conducted on patients with ovarian cancer (ovarian cancer) in China, researchers found that women who drank at least one cup of green tea per day lived longer with the disease than people who drank green tea. It even turned out that those who drank the most green tea lived the longest. But other studies found no beneficial effects.

Colorectal cancer

Clinical studies on the effects of green tea on colorectal or rectal cancer have shown conflicting results. Some studies showed a reduced risk in people who drank the tea, while other studies showed an increased risk. One study in which women drank five or more cups of green tea per day found that these women had a lower risk of colon cancer compared to non-tea drinkers. There appeared to be no protective effect for men. However, other studies show that drinking tea regularly may reduce the risk of colon cancer in women. More research is needed before researchers can recommend green tea for the prevention of colorectal cancer.

Esophageal cancer

Studies in laboratory animals have shown that the polyphenols in green tea inhibit the growth of esophageal cancer cells. However, human studies have produced conflicting findings. For example, in a large-scale population-based clinical trial, green tea was found to protect against the development of esophageal cancer, especially among women. Another population-based clinical study found just the opposite – green tea consumption was associated with an increased risk of esophageal cancer. Research showed; the stronger and hotter tea, the greater the risk. Given these conflicting results, more research is needed before scientists can recommend green tea for the prevention of esophageal cancer.

Lung cancer

As with esophageal cancer, studies have shown that the polyphenols in green tea can inhibit the growth of lung cancer cells in test tubes. Yet the same contradictions as with esophageal cancer also appeared to apply here.
More studies are needed before researchers can draw conclusions about green tea and lung cancer.

Research showed:

  • The combination of a standardized green tea extract and the cholesterol-lowering drug atorvastatin produced a clear synergy (they reinforce each other) in reducing the growth of lung cancer in mice and in various human lung cancer cell lines in cell culture.

Pancreatic cancer

In a large-scale clinical study, researchers compared green tea drinkers with non-drinkers and found that those who drank the most tea were less likely to develop pancreatic cancer. This was especially the case for women. The women who drank the most green tea were half as likely to develop pancreatic cancer as those who drank less tea. Men who drank the most tea had a 37% lower risk of developing pancreatic cancer. However, it is not clear from this population-based study whether green tea is solely responsible for lowering pancreatic cancer rates.
More studies in animals and humans are needed before researchers can recommend green tea for the prevention of pancreatic cancer.

Prostate cancer

Laboratory studies have shown that green tea extracts prevent the growth of prostate cancer cells in test tubes. In a large clinical study in southeastern China, researchers found that the risk of prostate cancer decreased with increasing frequency, duration and amount of green tea consumption.

Research showed:

  • In cell cultures with prostate cancer cells, EGCG appeared to promote the effect of chemotherapy (with taxol).

Stomach cancer

Laboratory studies have shown that the polyphenols in green tea inhibit the growth of stomach cancer cells in test tubes, but human studies are less conclusive. In two studies comparing green tea drinkers with non-drinkers, researchers found that people who drank tea were about 50% more likely to develop stomach cancer and stomach inflammation than those who did not drink green tea. However, a clinical study of more than 26,000 men and women in Japan found no link between green tea and stomach cancer risk. Some studies even suggest that green tea may increase the risk of stomach cancer.
More clinical studies are currently underway to see if green tea helps reduce the risk of stomach cancer.

Consult your doctor

Studies have also shown that both green and black tea extracts can stimulate genes that make cells less sensitive to chemotherapy drugs. So it is advisable for people undergoing chemotherapy to consult their doctors first before drinking green or black tea, or taking tea supplements.