Image Credit: Nathan Dumlao / Unsplash. This image has been modified.

Boosting Antiviral Immune Function with Green Tea

Unlike most antiviral drugs, green tea appears to work by boosting the immune system to combat diseases such as genital warts (caused by HPV) and the flu (caused by the influenza virus).

According to one study, “The belief in green tea as a ‘wonder weapon’ against diseases dates back thousands of years.” I’ve talked about it in relation to chronic disease, but what about infectious disease? I explore this in my video Benefits of Green Tea for Boosting Antiviral Immune Function. Interest in the antimicrobial activity of tea dates back to a military medical journal in 1906, which suggested that servicemen fill their canteens with tea to kill off the bugs that caused typhoid fever. “However, this effect of tea was not studied further until the late 1980s” when tea compounds were pitted against viruses and bacteria in test tubes and petri dishes, but what we care about is whether it works in people. I had dismissed this entire field of inquiry as clinically irrelevant until I learned about tea’s effect on genital warts. External genital warts, caused by human wart viruses, “are one of the most common and fastest-spreading venereal diseases worldwide.”

Patients with external genital warts “present with one or several cauliflower-like growths on the genitals and/or anal regions…associated with…considerable impairment of patients’ emotional and sexual well-being.” But rub on some green tea ointment, and you can achieve complete clearance of all warts in more than 50 percent of cases.

If it works so well for wart viruses, what about flu viruses? As you can see at 1:41 in my video, it works great in a petri dish, but what about in people? Well, tea-drinking school children seem to be protected, but you don’t know about the broader population until it’s put to the test. If you give healthcare workers green tea compounds, they come down with the flu about three times less often than those given placebo, as you can see at 2:02 in my video. In fact, just gargling with green tea may help. While a similar effect was not found in high school students, gargling with green tea may drop the risk of influenza infection seven or eight-fold compared to gargling with water in elderly residents of a nursing home, where flu can get really serious.

Unlike antiviral drugs, green tea appears to work by boosting the immune system, enhancing the proliferation and activity of gamma delta T cells, a type of immune cell that acts as “a first line defense against infection.” According to the researchers, “Subjects who drank six cups of tea per day had up to a 15-fold increase in [infection-fighting] interferon gamma production in as little as one week”—but why?

There is in fact a molecular pattern shared by cancer cells, pathogens, and “edible plant products such as tea, apples, mushrooms, and wine.” So, eating healthy foods may help maintain our immune cells on ready alert, effectively priming our gamma delta T cells so they “then can provide natural resistance to microbial infections and perhaps tumors.” I guess I shouldn’t have been so surprised; tea, after all, is a “vegetable infusion.” You’re basically drinking a hot water extraction of a dark green leafy vegetable.

For more on what green tea can (and cannot) do, check out videos such as:

How else can we improve our immune function? See, for example:

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.

52 responses to “Boosting Antiviral Immune Function with Green Tea

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  1. Are there any studies on whether green tea is effective against Covid-19? And what are your thoughts, if any, on green teas potential against COVID-19?

    My wife is a nurse who treats COVID patients. We both drink green tea every day and have not gotten sick.

  2. Are you recommending Fonte Green Tea Brand? Or will any label be okay? One of the dollar type stores has 100 bags of green tea for $1.00. Is flavored kind of green tea okay? There are many brands and kinds of green teas available with significant price variation. How can you tell if what you are drinking is the real stuff. The kinds I’ve tried had such a variety of taste including some tasteless, and others even unpleasant. Appreciate advice. Yes, I’ve had organic too.

    1. Sounds like you need to educate yourself about the quality of teas and how to infuse them properly. Tea, green, black, white, has a long history of use in Asia and is a tradition rich in custom, varietals, culinary and social use. The way most westerners dunk a cheap green tea bag in boiling hot water for five minutes is disrepectful to the tea. We don’t even begin to appreciate the sophistication surrounding green tea. I know, as I was one of those rubes who bought the cheapest brand and brewed the heck out of it and hated the taste but choked it down anyway because it was supposed to good for me.

      But a visiting Chinese friend gifted us a Yishing clay teapot and some really great chinese pu-er tea and taught us how to brew a cup properly. That was ten years ago. I have learned so much about tea since then and have come to appreciate it’s nuances and subtleties. I have settled on organic japanese sencha tea (brewed as loose leaf tea in a clay teapot…its a daily ritual) as my go-to daily tea, but still indulge in other varietals as my budget allows. I highly recommend this youtube channel of a London tea seller who is passionate about educating people about the enjoyment of tea and how to do it justice. All the videos are great. His enthusiasm and knowledge about tea is incredible.

      1. Mims, I didn’t enjoy the ceremony of tea in a clay teapot much myself. I use a large stainless strainer in a mug, but I do brew at the lower correct temperature.

      2. With all due respect Mims, long standing customs about tea drinking aren’t of much relevance to most of us..

        What I and I suspect many others are interested in are the health effects of tea drinking and how it is affected by the cultivar, its picking, its processing, storage, preparation and serving. Scientific studies are probably a better guide here than ancient customs and traditions.

        I seem to recall all the same sort of beliefs about the best wines, cigars, marijuana, craft beers, cuts of steak or whatever. They are all no doubt fascinating and absorbing interests and hobbies However, they are not necessarily a good guide to what is most healthy or even (at least in my experience) what is the most enjoyable way of consuming the items in question.

        it’s possible that green tea is like exercise – The best exercise is the one that you enjoy doing so that you are more likely to keep on doing it, day in day out and year in year out..The best green tea may be the one that you enjoy drinking the most.

        That said, I agree that research is essential. Lead contamination may be an issue with green tea and I understand that Indian teas have lower levels on average than Chinese and Japanese teas.

      3. Mims,

        I agree with you about green tea: I discovered, accidentally, that I like organic Japanese sencha tea best, even though I brew mine in a tea bag in a mug, at about 176 F (I have a temperature controlled pour-over electric kettle which I adore). It has a lovely light flavor and very pleasing aroma. To me, anyway.

      4. Mims, thanks for the suggestion of the youtube channel. Poped over to see what I’ve been missing. With all the health benefits of tea, may as well learn how to make it enjoyable.

    2. Hi Ruthie,

      I cold brew 2 bags of grocery store organic green tea with 1 bag of hibiscus tea in 28-32 oz filtered water for around 4 hours. I find if I forget and leave the bags in the water in the refrigerator overnight it gets too strong and develops a slightly bitter edge but that can be offset by simply adding a bit more water. The result is a delightful, bright, punch-like flavor; the best part is that no sweetener or additive is necessary—for either me or my teenaged daughter!

  3. My only problem with green tea is it makes me nauseous. Any advice on getting the benefits of green tea without the nausea?

    1. Joseph, you might try adding a generous pinch of powdered ginger, or perhaps a slice or two of fresh, to your brew and see if that helps with the nausea. Hope that helps!

    2. A few suggestion:
      1. Reduce the brewing time.
      2. Increase the amount of water.
      3. Use a creamer.
      4. Don’t drink to an empty stomach.

  4. Dr Greger, I take a teaspoon of macha powder plus a few herbs ( rosemary, cloves, turmeric, ginger, cayenne, cumin) etc and a few herbs in water everyday. Is the tea content enough?

  5. Thank you! One of my habits turns out to be good for me! For some reason, people have been giving me flack about drinking my mug of green tea every day. In addition to the immune system benefits, I find it calming. I started with Lipton tea bags. These days, I drink loose leaf green tea from India or white tea from China. While I like to get specific organic teas from Arbor Tea, you can find bulk tea leaves in many produce markets in cities. Like coffee, if you ask around, you will probably discover a local tea scene.

    1. You might want to click on the older presentation about arterial function. Black tea is good, but putting milk in it blocks the good effects. I don’t know if black tea is as good as green in all effects, but that was the story for that one.

  6. It should be mentioned that Green Tea is also an IONOPHORE (as it has QUERCETIN in it) this is what enables ZINC to get inside the CELL, which is essential during this pandemic
    Quercetin is a flavonoid that is found in many plant and foods such as onions, green tea, apples, peppers, and berries.

    1. Right, Patricia — this is a HUGELY IMPORTANT FACTOR. I’ve been reading one scientific paper after another about this online, already published papers or preliminary papers. The Facebook page for “Nutrition and Cytology” has been archiving a lot of these links for quick reference.

  7. Interesting comments today. I’m a bit of a tea snob myself – just re. personal use though; I have no interest in judging others tea habits. E.g. I like Japanese sencha OK, but the really ancient and highly developed traditions are more associated with Chinese teas.
    But I’d love to see a meta-study regarding the claimed benefits of different kinds and grades of tea, one not supported by any tea supplier. I’m aware of lots of bits of information but haven’t seen them collected in any single unbiased source. E.g. I’ve heard that black tea has benefits but that they’re different than those provided by green tea (which if true wouldn’t be too surprising given the very different levels of oxidation). Dr. Greger has provided some really valuable information regarding the benefits of tea, but if anyone is aware of a single source that weighs and compares the information provided by a variety of sources I’d love to hear about it.

    1. Ben,

      Dr. Greger has done a video on it and he has said that the beneficial vascular effects of tea are suppressed by soy milk.

  8. Any chemists out there? If I put 2 green tea bags in 6 oz of boiling water would it have the same nutrients as two cups of green tea, or will it get saturated or something that doesn’t happen when you use 1 tea bag in 6 oz of water?

    I don’t like the taste of green tea and thought making it supper strong I could drink less of it and get more benefit.

    1. Julia,

      We have had discussions about this on the site.

      Watch out for teas from China because of the lead.

      Japanese green tea – it depends on what section of the country. Tea from the Uji region, and the Yame, Kumamoto, Miyazaki and Kagoshima prefectures have not been found to have any radiation.

      Yes, those are not brand names, but they are things to look for.

      I bought a few brands but I am not recommending anything. I just looked for organic and where it was made.

  9. President of Madagascar is touting the benefits of sweet wormwood tea for viruses . It is extremely bitter but after trying it, I sort of like it , I;m thinking it helps digestion ?

    1. It’s supposed to be an effective anti-malarial.

      However, it interacts with a number of medicines and some animal studies suggest that it might also be neurotoxic.

      I personally wouldn’t want to drink it on a regular/long-term basis.

    2. It’s not the tea as such but an immunity-boosting tonic brewed from 65% artemesia annua and other plants which are being kept confidential for patent purposes. This tonic is to be taken for 7 days only and is not recommended for over-65s, people with high BP and kidney impairment, pregnant women and nursing mothers. A stronger version is used to treat Covid 19 patients but only in a medically supervised hospital environment.

    1. The process of decaffeinating the green tea removes some of the antioxidants. Not sure about whether it affects the whole gamma delta T Cell thing

  10. What about white tea? I read somewhere that white tea, which is the immature version of green tea, is even better than green tea for an anti-inflammatory effect. Plus, adding some lemon enhances both green and white tea. But, how much lemon? How much white tea and how often a day? For example, could drinking one large mug of 24 ounces of white tea with a few drops of lemon be enough? Thank you for searching out all the evidence-based info about what we eat and drink. Mary Beth Petersen

    1. While I’d like to provide you with definitive amounts of tea and lemon and clear distinctions between benefits of green v white tea, it seems white tea has not been studied enough yet to provide such specifics. I found one study that compared white and green tea, but it was in vitro, so although white tea showed more benefit in a test tube, we really can’t say it’s better in the human body. This study showed similar benefits for both: Antioxidant and antimicrobial activities of tea infusions “Green tea and white tea showed similar inhibitions of several microorganisms.” We also have to keep in mind how you brew your tea, as stronger tea would have more effect. Here is an article on recommendations on how to brew the white tea:

      As far as how much lemon, I’ve seen varied recommendations to obtain heath benefits from up to juice of 1 lemon to just a single slice. Again I could find no definitive study although research clarifying the benefits of lemon juice cited up to 1 oz of lemon juice/day as healthful. There are some concerns about too much lemon juice as the citric acid can he acids in lemon juice can cause gastrointestinal side effects causing upset stomachs if consumed in excess or aggravating gastrointestinal reflux disease (GERD. emon juice can also erode tooth enamel, so rinsing mouth and avoiding brushing just after consuming is recommended. Hope this is helpful. Enjoy your tea with lemon,green or white.

  11. I’m curious about your thoughts regarding white tea? It’s beginning to be studied more, and everything I’ve read indicates an even higher level of antioxidants and virus/bacteria fighting properties than green tea.

  12. Several reasons why Japanese people live such a long life (other than green tea).

    It’s interesting to watch them make tofu; also to see some people on the street donning masks even though this video was made at least two years ago.

    Also to watch one ol’ guy get his jollies from singing to people whether they wanted to listen to him or not. :-)

      1. And that was a VERY link! Notice how two of those schoolgirls showing their knees have the masks below their noses — the way I like to wear it when I can.

        Lots of cute designs on theirs too.

        1. Obviously, the omitted word was “interesting.” Sigh. We’re now in the shadow of the coming Mercury retrograde.

          This month of June and July are going to be HUGH, according to the astrologers. Many planets will be going nutsy, and unless we stay calm and carry on….so will we. :-(

  13. It’s always green tea, what about white tea? White tea is the least processed and its what I drink. Does white tea provide the same benefits as green tea?

  14. What are the ingredients of green tea? I drink a tea composed of cumin, coriander, fenugreek, and fennel. Would this be considered green tea? I obtained this recipe from another book ( the title escapes at this time).

    1. I don’t know what your drinking would be called but it’s not green tea. Green tea is a type of tea that is made from Camellia sinensis leaves and buds that have not undergone the same withering and oxidation process used to make oolong teas and black teas. White tea also comes from the same plant

  15. Isn’t green tea supposed to look green? The brands that I have tried yield beer yellow-brown color. Does the color matter? Can you recommend one or more brands that have a nice green color to make it more interesting? We are told to drink six cups of green tea in a day. If we use Matcha could we cut it down to 2 or 3 cups in a day? (I understand Match is a concentrated form of green tea.) I will appreciate the guidance. Thank you.

  16. Hello, Dr. Greger !

    Thank you for the great article !

    Please, create one article for camellia sinensis, the plant from which through process we obtain green tea.

    If green tea has so many benefits, what can we expect from camellia sinensis which is the unprocessed plant..?!

    Thank you !

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