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:

Risks vs. Benefits of Colonoscopies

Though colonoscopies can cause serious harm in about 1 in every 350 cases, sigmoidoscopies, procedures that use shorter and smaller scopes, have ten times fewer complications. But, do colonoscopies work better? Is their total risk-benefit better? We don’t know since we don’t have results from any randomized, controlled colonoscopy trials, and we won’t until the mid-2020s. So, what should we do in the meanwhile?

As I discuss in my video Should We All Get Colonoscopies Starting at Age 50?, the U.S. Preventive Services Task Force (USPSTF), the official prevention guidelines body, considers colonoscopies just one of three acceptable colon cancer screening strategies. Starting at age 50, we should either get our stool tested for hidden blood every year, which doesn’t involve any scoping at all; get a sigmoidoscopy every five years, along with stool testing every three; or get a colonoscopy every ten years. In terms of virtual colonoscopies or the new DNA stool testing, there is insufficient evidence to recommend either of those two strategies.

Though the USPSTF recommends ending routine screening at age 75, that assumes you’ve been testing negative for 25 years since your 50th birthday. If you’re 75 and have never been screened, then it’s probably a good idea to get screened at least into your 80s.

If there are three acceptable screening strategies, how should one decide? The USPSTF recommends that patients work with their physician in selecting one after considering each option’s risks and benefits. For patients to participate in the decision-making process, though, they have to be given the information. The degree to which health providers communicate the necessary information was not known until researchers conducted a study in which they audiotaped clinic visits looking for the nine elements of informed decision-making: discussing both the patient’s role and that role in making the decision, what kind of decision has to be made, the alternatives, the pros and cons of each option, and the uncertainties associated with the decision, as well as assessing the patient’s understanding and whether they desire input from those they trust, and, finally, asking them what they would prefer. That’s the role of a good doctor. It’s your body; it’s your informed decision.

How many of these nine crucial elements of informed decision-making were communicated to patients when it came to colon cancer screening?

Care to hazard a guess?

In most of the patients, none. The average number addressed? One out of nine. As an editorial in the Journal of the American Medical Association put it, “There are too many probabilities and uncertainties for patients to consider and too little time for clinicians to discuss them with patients.” So, doctors just make up the patients’ minds for them. And what do they choose? Most often, as in this survey of a thousand physicians, doctors recommend colonoscopy. Why? Other developed countries mostly use the stool tests, with only a few recommending colonoscopies or sigmoidoscopies. That may be because most physicians in the world don’t get paid based on how many procedures they do. As one U.S. gastroenterologist put it, “Colonoscopy is the goose that laid the golden egg.”

A New York Times exposé concluded that the reason doctors rake in so much money is less about “top-notch patient care” and more about business plans maximizing revenue, lobbying, marketing, and turf battles. Who sets the prices for procedures? The American Medical Association, the chief lobbying group for physicians, does. No wonder gastroenterologists pull in nearly a half-million dollars a year, and the American Gastroenterological Association wants to keep it that way. Referring to these exposés, the president of the association warned that “gastroenterology is under attack and colorectal cancer screening and prevention may be reduced in volume and discounted.” But, they then go on to share tips for how to succeed in the coming nightmarish world of accountability and transparency.

Why would primary care doctors push colonoscopies? Because many doctors get what are essentially financial kickbacks for procedure referrals. Studying doctor behavior before and after they started profiting from their own referrals, it’s estimated that doctors make nearly a million more referrals every year than they would have if they there were not personally profiting.


Serious harm in 1 out of 350 colonoscopies? See What to Take Before a Colonoscopy for all the gory details.

Too often, truly informed consent is a joke in modern medicine. For more on this, see:

How do you know if your doctor is on the take? Check out Find Out If Your Doctor Takes Drug Company Money.

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:

How to Ease the Pain of Colonoscopy

Peppermint was not “officially” discovered until 1696, but we’ve probably been using it for thousands of years. After-dinner mints are used to reduce the “gastrocolic reflex,” the urge to defecate following a meal. The stretching of nerves in the stomach triggers spasms in the colon, which makes sense because it allows us to make room for more food coming down the pipe. Peppermint, like in our after-dinner mints, relaxes the colon’s muscles. I explore this in my video What to Take Before a Colonoscopy.

When researchers took circular strips of human colon removed during surgery and laid them out on a table, they spontaneously contracted on their own about three times per minute. Isn’t that kind of creepy? But when more and more menthol from peppermint was dripped on them, the contractions still occurred but were not as strong.

If peppermint can relax the colon and reduce spasms, might it be useful during a colonoscopy, as first suggested 30 years ago? Colonic spasms can hinder the progress of the scope and cause the patient discomfort. So, researchers sprayed peppermint oil on the tip of the scope, and, in every case, the spasm was relieved within 30 seconds. Thirty seconds, however, is a long time when you have a scope snaking inside your colon. The next innovation was to use a hand pump to flood the entire colon with a peppermint oil solution before the colonoscopy, which caused the spasming colon to open up within 20 seconds. This is a simple, safe, and convenient alternative to injecting an anti-spasm drug, which can have an array of side effects.

Researchers saw similar results during upper endoscopy, with peppermint working better, quicker, and safer than drugs. Another study also found positive results when peppermint was mixed into barium enemas. But wouldn’t it be easier just to swallow some peppermint oil instead of squirting it up the rectum? Researchers looked at this alternative in a study using premedication with peppermint oil before colonoscopy. Just popping a few peppermint oil capsules four hours before the procedure sped up the entire process. Both doctor and patient satisfaction increased, because reducing colon spasms can reduce pain and discomfort as well as make the scope easier to insert and withdraw.

Pain and discomfort are not the only barriers to signing up people for colonoscopies, however. Even if peppermint oil makes the procedure go seamlessly, there’s still the dreaded bowel prep where you have to drink quarts of a powerful liquid laxative to completely clean you out before the colonoscopy. And, aside from the pain, there are also fears of complications and feelings of embarrassment and vulnerability.

Serious complications occur in about 1 in every 350 colonoscopies, including really serious complications like perforations and bleeding to death. Perforations can occur when the tip of the scope punches through the wall of the colon or when the colon is inflated too much while the doctor is pumping in air to look around. It can also happen while trying to cauterize bleeding caused by something like a biopsy. In extremely rare instances, this cauterization can ignite some residual gas and cause the colon to explode.

Death from colonoscopy is rare, occurring only in about 1 in every 1,000 procedures. But with about 15 million colonoscopies performed annually in the United States, colonoscopies may kill about 15,000 Americans every year. This raises the question whether the benefits outweigh the risks? I was shocked to find out how risky colonoscopies are, but dying from colon cancer is no walk in the park either. There’s got to be a better way, and I cover that topic in my Should We All Get Colonoscopies Starting at Age 50? video.


Read more on iatrogenic (doctor-induced) risks of various medical procedures in my videos:

You can also learn more about the benefits of all kinds of mint in these videos:

And what about preventing colon cancer in the first place? 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: