Using Green Tea to Help Prevent Cancer and Treat Cancer

Tea consumption is associated with a reduced risk of heart disease, stroke, and premature death in general, with each additional cup of green tea a day associated with a 4-percent lower mortality risk. So, perhaps “drinking several cups of tea daily can keep the doctor away,” as well as the mortician—but what about cancer?

As I discuss in my video Can Green Tea Help Prevent Cancer, there is “growing evidence from laboratory, epidemiologic [population], and human intervention studies that tea can exert beneficial disease-preventive effects” and, further, may actually “slow cancer progression.” Let’s review some of that evidence.

Not only do those who drink a lot of tea appear to live longer than those who drink less, as you can see at 0:49 in my video, drinking lots of tea may also delay the onset of cancer. At 0:56 in my video, you can see a table titled “Average age at cancer onset and daily green tea consumption.” The green tea intake is measured in Japanese tea cups, which only contain a half a cup, so the highest category in the table is actually greater than or equal to five full cups of tea, not ten as it appears in the table. Women who did get cancer appeared to get it seven years later if they had been drinking lots of tea compared to those who had consumed less. Men, however, had a three-year delay in cancer onset if they had consumed more than five full cups of green tea daily, the difference potentially “due to higher tobacco consumption by males.”

Green tea may be able to interfere with each of the stages of cancer formation: the initiation of the first cancer cell, promotion into a tumor, and then subsequent progression and spread, as you can see at 1:24 in my video. Cancer is often initiated when a free radical oxidizes our DNA, causing a mutation, but, as you can see at 1:44 in my video, we can get a nice “spike of antioxidant power” of our bloodstream within 40 minutes of drinking green tea. “This increase may, in turn, lower oxidative damage to DNA and so decrease risk of cancer.”

Furthermore, in terms of genoprotective effects—that is, protecting our genes—pre-existing oxidation-induced DNA damage was lower after drinking green tea, suggesting consumption can boost DNA repair as well. We didn’t know for certain, however…until now.

There is a DNA-repair enzyme in our body called OGG1. As you can see at 2:15 in my video, within one hour of drinking a single cup of green tea, we can boost OGG1’s activity, and after a week of tea drinking, we can boost it even higher. So, “regular intake of green tea has additional benefits in the prevention and/or repair of DNA damage.” In fact, tea is so DNA-protective it can be used for sperm storage for fresh samples until they can be properly refrigerated.

What’s more, tea is so anti-inflammatory it can be used for pain control as a mouthwash after wisdom tooth surgery, as you can see at 2:41 in my video. In terms of controlling cancer growth, at a dose of green tea compounds that would make it into our organs after drinking six cups of tea, it can cause cancer cells to commit suicide—apoptosis (programmed cell death)—while leaving normal cells alone. There are a number of chemotherapy agents that can kill cancer through brute force, but that can make normal cells vulnerable, too. So, “[g]reen tea appears to be potentially an ideal agent for [cancer] prevention”: little or no adverse side-effects, efficacious for multiple cancers at achievable dose levels, and able to be taken orally. We have a sense of how it works—how it stops cancer cells from growing and causing them to kill off themselves—and it’s cheap and has a history of safe, acceptable use. But, all of this was based on in-vitro studies in a test tube. “It needs to be evaluated in human trials,” concluded the researchers. Indeed, what happens when we give green tea to people with cancer? Does it help?

Tea consumption may reduce the risk of getting oral cancer. Not only may the consumption of tea boost the antioxidant power of our bloodstream within minutes and decrease the amount of free-radical DNA damage throughout our systems over time, but it can also increase the antioxidant power of our saliva and decrease the DNA damage within the inner cheek cells of smokers, though not as much as stopping smoking all together. You can see several graphs and tables showing these findings in the first 35 seconds of my video Can Green Tea Help Treat Cancer?.

Might this help precancerous oral lesions from turning into cancerous oral lesions? More than 100,000 people develop oral cancer annually worldwide, with a five-year overall survival rate of less than the flip of a coin. Oral cancer frequently arises from precancerous lesions in the mouth, each having a few percent chance of turning cancerous every year. Can green tea help?

Fifty-nine patients with precancerous oral lesions were randomized into either a tea group, in which capsules of powdered tea extract were given and their lesions were painted with green tea powder, or a control group, who essentially got sugar pills and their lesions painted with nothing but glycerin. As you can see at 1:23 in my video, within six months, lesions in 11 out of the 29 in the tea group shrunk, compared to only 3 of 30 in the placebo group. “The results indicate that tea treatment can improve the clinical manifestations of the oral lesions.”

The most important question, though, is whether the tea treatment prevented the lesions from turning cancerous. Because the trial only lasted a few months, the researchers couldn’t tell. When they scraped some cells off of the lesions, however, there was a significant drop in DNA-damaged cells within three months in the treatment groups, suggesting that things were going in the right direction, as you can see at 1:46 in my video. Ideally, we’d have a longer study to see if they ended up with less cancer and one that just used swallowed tea components, since most people don’t finger-paint with tea in their mouths. And, we got just that.

As you can see at 2:15 in my video, there were the same extraordinary clinical results with some precancerous lesions shrinking away. What’s more, the study lasted long enough to see if fewer people actually got cancer. The answer? There was just as much new cancer in the green tea group as the placebo group. So, the tea treatment resulted in a higher response rate, as the lesions looked better, but there was no improvement in cancer-free survival.

These studies were done on mostly smokers and former smokers. What about lung cancer? As you can see at 2:46 in my video, population studies suggest tea may be protective, but let’s put it to the test. Seventeen patients with advanced lung cancer were given up to the equivalent of 30 cups of green tea a day, but “[n]o objective responses were seen.” In a study of 49 cancer patients, 21 of whom had lung cancer, the subjects received between 4 and 25 cups worth of green tea compounds a day. Once again, no benefits were found. The only benefit green tea may be able to offer lung cancer patients is to help lessen the burns from the radiation treatments when applied on the skin. Indeed, green tea compresses may be able to shorten the duration of the burns, as you can see at 3:21 in my video.

The protective effects of green tea applied topically were also seen in precancerous cervical lesions, where the twice-a-day direct application of a green tea ointment showed a beneficial response in nearly three-quarters of the patients, compared to only about 10 percent in the untreated control group, which is consistent with the benefits of green tea compounds on cervical cancer cells in a petri dish. When women were given green tea extract pills to take, however, they didn’t seem to help.

I talked about the potential benefit of green tea wraps for skin cancer in Treating Gorlin Syndrome with Green Tea, but is there any other cancer where green tea can come into direct contact? Yes. Colon cancer, which grows from the inner surface of the colon that comes into contact with food and drink. As you can see at 4:13 in my video, in the colon, tea compounds are fermented by our good gut bacteria into compounds like 3,4DHPA, which appears to wipe out colon cancer cells, while leaving normal colon cells relatively intact in vitro. So one hundred thirty-six patients with a history of polyps were randomized to get green tea extract pills or not. Now, this study was done in Japan, where drinking green tea is commonplace, so, effectively, this was comparing those who drank three cups of green tea a day to subjects who drank four daily cups. A year later on colonoscopy, the added-green tea group had only half the polyp recurrence and the polyps that did grow were 25 percent smaller. With such exciting findings, why hasn’t a larger follow-up study been done? Perhaps due to the difficulty “in raising funds” for the study, “because green tea is a beverage but not a pharmaceutical.”

There is good news. Thanks to a major cancer charity in Germany, researchers are currently recruiting for the largest green tea cancer trial to date, in which more than 2,000 patients will be randomized. I look forward to presenting the results to you when they come in.


What about prostate cancer? See my videos Preventing Prostate Cancer with Green Tea and Treating Prostate Cancer with Green Tea.

You may also be interested in these somewhat older videos:

How interesting was that about wisdom teeth? Green tea can also be used as an anti-cavity mouth rinse, which I discuss in my video What’s the Best Mouthwash?.

Is Caffeinated Tea Dehydrating? Watch the video to find out.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Is Triclosan Antibacterial Toothpaste Safe?

Why do dogs lick their wounds? They even lick our wounds. This leads to a question posed in the medical literature nearly a half century ago: Might there be some healing property of dog saliva? Well, it appears that there are a number of immune defense mechanisms in saliva, one of which involves nitric oxide. Licking of human skin results in production of nitric oxide from salivary nitrite, which kills skin pathogens and comes from the nitrates we eat in our diet.

How do we know we can get nitric oxide from licked human skin? Researchers had a bunch of volunteers lick their hands all over, front and back. Today, we have a better way to clean wounds: soap and water. (And we should never let our pets lick open wounds because cases of serious infections have been reported).

The reason I bring it up is that this transformation of nitrates from our diet into nitrites in our mouth has important implications for our health. Insufficient nitric oxide production is recognized as the earliest event in the onset and progression of a number of chronic diseases, including high blood pressure, peripheral artery disease, and a number of inflammatory conditions.

Nitrates come from vegetables in our diets, such as beets and green leafy vegetables. Good bacteria on our tongue convert nitrates into nitrites which can circulate throughout the body to create nitric oxide, and any nitrates our tongue bacteria missed the first time around get pumped by our body back into our saliva to give our tongue bacteria a second chance. One way we can become nitric-oxide-production-deficient is by not eating enough vegetables in the first place. So, eating vegetables should be the first step. But, if our tongue bacteria die off, the cycle is broken no matter how many vegetables we eat.

That’s why we should not use antiseptic mouthwash. Previously, I profiled an important study in my video Don’t Use Antiseptic Mouthwash. The most protective food for our heart may be green leafy vegetables because, like beets, they have lots of nitrates. So, if you drink some beet juice, you can get a remarkable drop in blood pressure within just hours, but only if you swallow.

The nitric oxide pathway can be interrupted if you use an antibacterial mouthwash or by spitting and not swallowing beet juice because of the critical action of our tongue bacteria on the nitrates in our saliva. So, we have to eat our vegetables and keep our tongue bacteria happy––so, no antibacterial mouthwash. But what about antibacterial toothpaste?

There’s a toothpaste on the market that contains an antibacterial chemical called triclosan. In my video Antibacterial Toothpaste: Harmful, Helpful, or Harmless?, I present a study was done that showed there was no difference in the levels of nitric oxide, nitrite, and nitrate after brushing with regular toothpaste and triclosan toothpaste. Our good tongue bacteria live in the cracks on the surface of our tongue, so if you just brush your teeth and not your tongue, the chemical doesn’t seem to get down there. Does that mean triclosan toothpaste is safe?

The use of triclosan toothpaste may not be associated with any increase in serious adverse cardiac events. And though studies on rats suggest the chemical can affect thyroid function, the use of triclosan toothpaste does not seem to affect human thyroid function. A study funded by Colgate concluded that triclosan was both safe and effective, producing “a significant reduction in gingivitis, plaque, and bleeding.” However, an independent review by the Cochrane Group suggested the reduction may be statistically significant but may not be beneficial enough to yield clinical significance.

Regarding safety, states are starting to ban the stuff because of data showing that despite the lack of efficacy, triclosan is so ubiquitous that most of the U.S. population is exposed to it. “Because the rapid rise in obesity in the U.S. parallels the introduction of triclosan, and because triclosan has two potential mechanisms by which it might alter human weight”—that is, by mucking with our gut flora or our hormones––researchers at Stanford decided to assess the association between triclosan levels flowing through people’s bodies and how heavy they are. And, indeed, they found an association between triclosan levels and increase in body mass index, and suggested further studies on how this chemical could be altering human growth and well-being.


If we shouldn’t use antiseptic mouthwash, What’s the Best Mouthwash? (Spoiler alert: It’s green tea!)

I’ve created an extensive video library on the benefits of nitrate-containing vegetables for both athletic performance and cardiovascular benefits. Here are some of the latest:

For more on nontoxic ways to maintain oral health, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: