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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:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

59 responses to “Using Green Tea to Help Prevent Cancer and Treat Cancer

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      1. I am interested in the caffeine, period. I stopped drinking caffeinated coffee (4-6 cups a day) to decaf because I was sure it was affecting my sleep and blood pressure. But, if I were drinking 5 cups a day of (mostly cold) green tea (which I used to do), I am wondering how the caffeine would affect my sleep and BP.

        So, is the caffeine in green tea a problem?

        I can’t seem to find decaf green tea although I don’t think I ever looked.

    1. At least some studies have shown that the caffeine from tea can be removed and nutrients are unaffected. Extraction and removal of caffeine from green tea by ultrasonic-enhanced supercritical fluid. Note that this result seems to depend on the HOW the caffeine is removed, which brings up some complicating factors, including harmful solvents used during some decaffeinating processes. From the research I’ve read the green tea would work as well, but finding out how your green tea is decaffeinated may be challenging. .

      1. Joan Nurse-Educator, who is one of our volunteers, addressed that question above. “At least some studies have shown that the caffeine from tea can be removed and nutrients are unaffected. Extraction and removal of caffeine from green tea by ultrasonic-enhanced supercritical fluid. Note that this result seems to depend on the HOW the caffeine is removed, which brings up some complicating factors, including harmful solvents used during some decaffeinating processes. From the research I’ve read the green tea would work as well, but finding out how your green tea is decaffeinated may be challenging.” I hope that helps!

  1. As far as I have studied there is a big difference between Japanese Green Tea and Chinese Green tea, I have not seen anyone identify these differences yet, please could you take a look rather than just stating ‘Green Tea’, the results would be useful for many people.

    1. You’re right that there are differences in the way tea is processed in China and Japan and maybe that makes s difference, but it is all Camellia sinensis after all…

      1. It’s possible to buy green tea from Ceylon (Sri Lanka) and India. Or from anywhere that tea is grown for that matter.

    1. fredroberts,

      Hibiscus tea doesn’t have a situation where whole populations are drinking it enough to do the same studies, so there won’t be the same type of study.

      Dr. Greger does have a hibiscus tea video though.

      1. It’s that Hibiscus video that leads me to ask the question. The video suggests that Hibiscus tea is superior to Green Tea, but does not discuss cancer specifically.

  2. I am not a tea lover but do add matcha powder to my green drink every morning. Are the benefits of powder the same as drinking the tea?
    Thanks so much!

  3. Something doesn’t agree with me when I drink green tea. I get nauseated very badly. I tried to consume it with food rather than on an empty stomach, but it doesn’t help. Is there a recommendation or suggestion what else to try? I’d love to drink green tea.
    I’m also interested in the matcha powder answer to the question posted above. Thank you

    1. Sourcing tea is important….some sources are full of toxins and heavy metals, even organic ones. I am still researching the best place to get it, you could call the company and ask if they have done third party testing for toxicity. It is complicated but worth it to find a clean, reputable source. I am also wondering if Puerh tea has the same effects. It is lower in caffeine and does not make me as nauseated as Matcha. It is harvested from the same plant but fermented longer and is also supposed to be really good for you. Does it have EGCG’s as well? It is also much smoother and has no bitterness, very pleasant tasting tea.

    2. Melanie,
      There are so many types of green tea; in tea bags they tend to put “tea dust” which is very harsh. Try ordering online from a quality tea provider, like Upton Tea. I have been using them for years and they will send you samples. Reasonable prices also.

  4. Reading this again, it is interesting that it helps pre-cancerous lesions while not preventing cancer.

    I do wonder if it at least might slow the growth of the cancer.

    I had 2 friends who had serious problems with fibroids for so long that they were being told their only option was surgery. That was what several specialists said.

    I found a green tea extract study and said, “Maybe you could try drinking green tea” and both of them never mentioned it again and never had surgery.

    It went from agony to a non-issue.

  5. Uh cheap… let’s go with cheap relative to medical costs. I’ve developed a not so cheap habit re. relatively high grade Chinese Dragonwell (though obviously reaping the green tea benefits doesn’t require one to shell out for something like that).

    1. With the extreme human abuse and outright global criminality of the Chinese Communist Party, I refuse to purchase anything that was either mad or assembled in China.

  6. I vote for you to be the next head of the next international health organization.
    You speak if health, healthy food and free choices.
    As opposed to the current WHO, that just spew fear, mandatory vaccines and control.

    1. In the US, the CDC says that there is 94% comorbidity for virus deaths. Many of those cofactors are caused by the SAD diet. Obesity, cardio, type 2, chronic kidney disease.

  7. I make a smoothy in the morning with spinach, banana, blue berries and ice and a squeeze of lemon. If I add green tea powder to this will I still benefit from it? I recall there being a study that said adding milk (soy, oat, almond…) to green tea can inhibit its benefits and lemon boosts them. I am not a fan of the taste of green tea so if I can benefit from it hiding it in my morning smoothy I would be thrilled. Am I good to go?

    1. hi TR ,
      Your morning drink sounds wonderful! There is an older video that talks about lemon enhancing properties in white tea enough to make it as healthful as the green tea,
      so it sounds like a winning combination.

      Please read the article linked below about lead in tea leaves. No need to panic though because Dr Greger explains safe quantities, sourcing, differences between black and green. And you are correct in not adding milks … the proteins can nullify the benefits.

      I do not care for hot green tea at all, but I tried Dr Greger’s idea of cold brewing green tea in the fridge.
      Tastes like cold refreshing water.. no bitterness!

      1. thank you for all the information. I am looking now to see can we test these things at home? lead in our tea? arsenic levels in our brown rice? cadmium in dark chocolate… I feel terrible throwing away food.

    2. Adding green tea is fine as long as you don’t need the iron. Most men have too much iron so it’s a non issue for men. But menstruating women might want to not inhibit iron absorption. Green tea can inhibit iron absorption.

    3. Tea often contains heavy metals like lead and cadmium. Only a percentage of those metals leaches into the infusion when we make tea drinks. The leaves are then discarded..

      If however we eat heavily processed entire tea leaves (chopped into very small pieces as in matcha tea or in a blender), we are likely to absorb significantly higher amounts of heavy metals from tea.

      Just a factor to consider.

    4. I include flax seeds, sesame seeds, and chia seeds in my smoothies, in addition to walnuts and peanut butter. They add bulk, in addition to nutrition. Not too much chia seeds, as they can cause constipation.

  8. Good morning – my question is about your offer of the Evidence Based Eating Guide if you become a subscriber to your newsletters. I’ve been a subscriber for quite a few years and would enjoy getting a copy of the EBEG myself. Is that possible? Thank you for your consideration of my request.

    On the topic of green tea; we have been drinking green tea for quite a few years and truly enjoy it! We have friends in Nagoya-shi Japan and every now and then, they send us a couple bags…what a treat & what a difference! They suggested we could “re-use” our leaves a second and sometimes a third time which is fantastic! Each cup after the 1st is decaffeinated which is easier on my husband’s system (he has a low tolerance of caffeine). Are the following cups as powerful as the first when it comes to helping fight cancer or do they all have to contain caffeine? Taking into consideration that the amount of caffeine found in green tea is much lower than other teas and coffee, is that an issue?

  9. I have always wanted to switch from Indian black tea to green tea. But could anyone or Mr. Greger himself suggest what kind of green tea is best and the best method of preparation of green tea drink? Also would mixing in Almond milk reduce or destroy its beneficial properties? Thanks.

  10. I don’t know the medical efficacy of the variation, however, I put the contents of a bag of green tea in my smoothie every other day and Hibiscus tea in my smoothie on the alternating days. It would be interesting to know if the consumption of the actual tea leaves are better or worse in their effectiveness.

    1. I do something similar. I use my spice grinder to turn green tea leaves and hibiscus leaves into powders and add both to my vegan morning smoothie. I wiki-looked up matcha tea and found that there is more to making matcha than just turning green tea leaves to powder. But still, the anti-oxidant power of both powdered green tea and hibiscus should be healthful anyway.

  11. I dislike lemon in my tea, but I do add lemon juice to white tea with a little honey.

    1. I love green tea, and would love to drink 5-6 cups a day, but I have interstitial cystitis. Any kind of tea (or coffee) irritates the bladder. How can I get the green tea benefit without actually drinking it? I hope the good doctor will answer this question! Thank you, Michele

      1. As you may know supplements generally are not looked upon favorably in this site see so I usually would’t encourage them. However, many of the studies citing the benefits of green tea use green tea extracts (instead of just the tea itself) and many show similar benefits from green tea itself, for ex:
        Effects of medium-term green tea extract supplementation combined with CrossFit workout on blood antioxidant status and serum brain-derived neurotrophic factor in young men: a pilot study.
        You may want to try extracts to see if they cause bladder irritation and if not that may be one way to get that green tea benefit without the full green tea. Of course eating other plant based whole foods are also great at providing those benefits, so if you don’t do green tea you still can find those benefits, even if it’s not quite as easy as just drinking tea. It’s a good goal for you to work on and I congratulate you for your efforts.

    2. Hi Andy, that combination of lemon and honey and white tea sound like a good drink. I think it is individual taste how much lemon you like to add to your tea. Lemon and white tea both have antioxidant properties.I have not found a study to find out how much lemon is required for maximum benefit. One has to be cautious of acidity of a drink on the teeth enamal too.

  12. Dr. Greger was interviewed on the Physician’s Committee site today.

    They have been doing videos every day and Chef AJ has been doing a lot of videos.

    And, the Science Music Video guy is teaching his classes online live twice a week.

    I feel like I won the lottery. So many amazing things to watch online.

  13. Aren’t there concerns about green tea inhibiting nutrient absorption from food? That’s why I don’t drink it more often than occasionally. I otherwise enjoy it a lot. I enjoy hibiscus tea daily, with added fresh grated ginger and a dash of ground cloves. As I think (scary, yes) it seems like there are concerns about ginger blocking nutrients from food too!

    1. Maybe in the lab, but our major concern is “hard clinical endpoints” like rates of disease and premature death. Populations that consume things like tea and ginger live longer and have less disease than those that don’t consume them. That’s what we focus on.

  14. My aspiration is to live long enough to see Scotland win the world cup. I am naturally delighted with Dr Greger’s comment;

    “with each additional cup of green tea a day associated with a 4-percent lower mortality risk”

    So, it’s 25 cups of green tea a day for me from here on and if I keep that going maybe I’ll see Scotland win three world cups :-)

    All the best


  15. I’m curious about decaffeinated green tea. I have blood pressure issues and try to limit my intake of caffeine. Do you loose any of the benefits using decaffeinated green tea? Thanks

    1. Here’s one study that tested antioxidant levels and found while there was a reduction from regular to decaffeinated green tea it was not that much:
      Catechin Content of 18 Teas and a Green Tea Extract Supplement Correlates With the Antioxidant Capacity
      (Trolox equivalent antioxidant capacity (TEAC) is a measurement of antioxidant strength)
      Hope this is reassuring as you enjoy your next cup or decaf green tea!

  16. as you well know,if it cannot be patented and profits to be made, there will never be a clinical trial of green tea or any other natural herb/food/supplement. It is very easy to get rid of cancer but you will never see your doctor in the US telling you how to do it, all they know is (cut, burn and poison) because if the y do it they will loose their license. Very good article, I admire your work Dr. Greger.

  17. So now its ok to cite an industry sponsored study?
    Studies have shown green tea is not better than hot water.
    the studies were sponsored by the tea industry.
    Just like the meat and dairy industry studies you debunk.
    I am a vegan. I will tell you why green tea is healthy. For the same reason Fish is healthy.
    When you replace red meat or chicken with 60% water Fish which makes you full faster you see health improving because of a reduction of 40% of meat in the diet. Not because fish is healthy.
    Same ways when people switch to green tea they tend to have it without sugar and Milk.
    the health improvements we see is from skipping dairy and refined sugar.

  18. Hi, Dr. Greger,

    I have an autoimmune disease (Hashimoto’s) and I noticed that whenever I drank green tea (or took elderberry), I got increased symptoms of the disease (in my case, extreme fatigue and hair loss). This usually happens if I take it once a day for more than two weeks. I was wondering if immune-boosting teas and products might also “boost” autoimmunity.

    I honestly did not even realize that there was a correlation until I was searching “Hashimoto’s sudden extreme fatigue) and someone mentioned green tea causing their fatigue. Then, I realized I’d been drinking it every day for a month and that this was the same problem I had with elderberry.

  19. Regarding this article…

    Can anyone recommend a good quality decaf green tea? I’m curious what the difference is between an off the shelf green tea brand like lipton or whatever, and a “higher quality” or better sourced tea.
    I have a fair caffeine sensitivity, so I’d definitely prefer something very low in caffeine or just plain decaf.

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