Doctor's Note

For more on tea, check out these videos:
Is There Too Much Aluminum in Tea?
How Much Hibiscus Tea is Too Much?
Better Than Green Tea?

And check out my other videos on tea

For further context, also see my associated blog posts: Eating To Extend Our the first month; and Soy milk: shake it up!

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  • Hi Good Doctor…i read the link
    …Ok It seems some people’s body can’t handle the Therapeutic Kombucha…but the scientific studies I sent you above(link below) seem to indicate a larger truth that IT won’t harm you and be beneficial . i find it odd that your nicely presented report is biased and not balanced..from meeting you in Montreal I found you objective but what I get from your link and the non inclusion of the scientific studies as noble as the one you refer to
    is that you are into shock news rather than balancing the reporting of the studies you select…PLS correct your unbalanced report on Kombucha if you want to be helpfull rather than an alarmist…

    • Michael Greger M.D.

      Kombucha may indeed reduce the organ damage of irradiated rats, but not sure the relevance (unless you have a pet rat and your friendly neighborhood nuclear plant melts down?). As a physician I’m kind of a rather limited veterinarian–I only know about one species! But I’m not saying there aren’t benefits to kombucha consumption, I’m just saying that if you look at a systematic review of the clinical evidence the benefits may not outweigh the risks. In fact, why tolerate any significant risks in our diet? That’s why I have a low tolerance for recommending against the consumption of foods shown to have serious adverse effects.

      • I think it’s a little much to state that, based on 3 adverse reports (with no data about those cases at all) that there is too much risk in drinking kombucha. Maybe the issue lies in proper preparation. There are also rumors stating that lavender and tea tree oil lead to hormonal issues in boys, but that was based on 3 kids as well and wasn’t a study at all. Furthermore, I have heard that reports on PubMed can simply be paid for and put there. So we need to look at “evidence” there with an open, yet questioning, mind. I’d love to hear what you think about my points. Thank you.

      • Jen

        “I’m just saying that if you look at a systematic review of the clinical evidence the benefits may not outweigh the risks”

        Couldn’t you say this about nearly any food? Our ENTIRE diet is LOADED with significant risks. Remember when people were getting salmonella from spinach? 33 deaths from Listeria in Cantaloupes last year? Processed foods and soda which harden arteries and kill you slowly?

        ” In fact, why tolerate any significant risks in our diet? That’s why I have a low tolerance for recommending against the consumption of foods shown to have serious adverse effects.”

        Doc,I do NOT want to tolerate risks in my diet. However, as a health professional I would prefer if your public health education program was more focused on the mainstream, rather than the minority. We have so many other problems!

  • mica_m

    So the paper displayed here says ‘A Case Of Kombucha Tea Toxicity’. Was this literally one case? Or are there others? I can’t find much info aside from various references mentioning a single ‘rare case of myositis’ – this does not in anyway imply some kind of serious risk here. We do not know what else was going on with this ‘single case’ – did this person have other health issues? Was they on certain medication (known to cause lactic acidosis)? There can be a number of causes:

    An awful lot of people drink Kombucha (some on a daily basis). This sounds like a statistical anomaly.

    • Michael Greger M.D.

      This was just a case report (which means by definition just one patient is described), but as I noted above, a systematic review concluded the benefits may not outweigh the risks. This was just one of the latest cases. It’s certainly an extremely rare consequence of kombucha consumption, but just like with medications, even though side effects can be rare, one still has to balance the benefits and risks. So I’d much rather see people drink (green or white) tea straight, which has more proven benefits and fewer reported risks.

      • j j

        how do you feel about kefir? safe? there are several vegan options of kefir available.

      • Quite happy to be natural

        I find your position a bit funny given the way perscription drugs are perscribed at the massive number of lawsuits concerning them. Heck the bulk ogf my health issues were caused by the use of antibiotics. Fosomax was a difinant contributing factior in my moms death…didn’t know it until years later when the link was found between that drug and heart issues, which my mother never had until she started taking fosomax. My neighbors mom started haveing issues after taking fosomax, her dr. told her she was haveing panic attactks. Hah! nope it was the fosomax. The drug side effects are rediculous! Talk about the benefit not outwaying the risk. Far more risks to drugs than consuming kombucha. I love what Kombuchas has done for me! Crazy how easily dr. poo poo natural remedies and go nuts over the limited number of side effects but the industry won’t hardly admit to the side effects of drugs and especially the possibility that there are issues with immunizations…Hum interesting that the gov’t has the immunization injury fund…I wonder why that is!

        • sf_jeff

          Dr. Gregor does not seem the type of doctor to routinely over-medicate.

  • Thanks for comments Doctor..Granted …Foods have risks..and if you Got AIDS you need to be careful about what you drink…carefully made Kombucha is a health drink that is therapeutic and needs to be consumed with the understanding of possible side effects…The Kombucha I drink has been very helpful for me as my digestive system not so great…but caution in consumption quantity at start if Novice is needed especially if you have AIDS…as outlined in you toxicity study link above.

  • Ethan

    What about the beneficial pro-biotic organisms and EGCG in kombucha? If someone is able to balance their pH by consuming more alkaline foods, wouldn’t its consumption be justified?

  • omnimatty

    I am greatly enjoying your website and all of your videos and information. Thank you for all of the work you are doing. Is there a better alternative for the kombucha? My wife loves it, but If I could offer her a more healthful replacement, that would be excellent. 

  • Soniin

    I make and drink kombucha on a daily basis and give away the scobies to friends to start their own batches.  I think this article and doctor are ridiculous to suggest it is harmful.  As usual, anything rich in life and probiotics, are deemed harmful by the medical association, who would rather dispense drugs than actually give something helpful to a person.  BUT, Do no harm…. what a crock of ****

    • Toxins

      In the words of Jeff Novick

      “While Kombucha tea is widely promoted to have miraculous medicinal
      properties, there is no evidence that Kombucha tea is effective for any
      of the reasons it is promoted for.

      What is being sold as Kombucha today is a colony of numerous species
      of fungi and bacteria living together, which permeate the tea. The
      precise composition of any sample of Kombucha depends to a great extent
      on what was floating around in your kitchen when you grew it or the
      kitchen (room) where it was grown.

      The most common microorganisms found in Kombucha tea include species
      of Brettanomyces, Zygosaccharomyces, Saccharomyces, Candida, Torula,
      Acetobacter, and Pichia. However, some analyzed specimens have been
      found to contain completely different organisms, and there is no
      guarantee that they will be harmless.

      In addition, there are case reports, which suggest that Kombucha
      preparations can cause such problems as nausea, jaundice, shortness of
      breath, throat tightness, headache, dizziness, liver inflammation, and
      even unconsciousness.

      Mayser P, Fromme S, Leitzmann C, et al. The yeast spectrum of the ‘tea fungus Kombucha’. Mycoses. 1995;38:289-295.

      Food and Drug Administration. FDA cautions consumers on “Kombucha
      Mushroom Tea” {News release}. Washington, DC: US Department of Health
      and Human Services, Public Health Service, Food and Drug Administration,
      March 23, 1995

      CDC. Anticholinergic poisoning associated with an herbal tea — New York City, 1994. MMWR 1995;44:193-5.

      Srinivasan R, Smolinske S, Greenbaum D. Probable gastrointestinal
      toxicity of Kombucha tea: is this beverage healthy or harmful? J Gen
      Intern Med. 1997;12:643-644.

      Unexplained severe illness possibly associated with consumption of
      Kombucha tea—Iowa, 1995. From the Centers for Disease Control and
      Prevention. JAMA. 1996;275:96-98.

      Perron AD, Patterson JA, Yanofsky NN. Kombucha “mushroom” hepatotoxicity. Ann Emerg Med. 1995;26:660-66

      Sadjadi J. Cutaneous anthrax associated with the Kombucha “mushroom” in Iran [letter]. JAMA. 1998;280:1567-1568.

    • Carrie

      What a ridiculous statement on your part…. To lump Dr. Gregor with the medical community as a whole shows only your ignorance. Please resist the urge to share future responses unless you are truly informed and not just looking to throw ridiculous jabs because something doesn’t agree with your ideas.

  • Mirna

    Doctor G, I love your site, but I read that Kombucha naturally produces B12 (among other things). Is this true, because I’m ready to send a sample of my own brew to get it tested. If true, this is fantastic news!

    Also, the animal tests don’t mean anything to me…I’m not a rat, pig, rabbit or dog and all those tests proved it to be unsafe. As an example; there are a number of toxic things my dog can’t eat, but onions and almonds are safe for humans. :)

  • dohduh

    What about the Cornell study? Sorry to use a commercial site, but this was the only version I could find that was more than an abstract. Granted it is from 2000, but the death of the woman often referenced was in 1995.

    • Toxins

      Because something has antimicrobial properties does not necessarily mean it is healthy for you, as we can see with alcohol. The study Dr. Greger presented is independent of this antimicrobial property so it shouldn’t matter as there is no dispute.

  • olothstar

    What about water kefir ? i have been making my own kefir with water kefir grains since i turned vegan to help get the probiotic i used to get in my yogurt. i don’t see any serious studies about it; have you come across any ?

    thanks for all your great work !

  • Occams_Razor

    This is fun learning at its best. I am still attempting to learn about vitamins, with a bit of fence-sitting about giving them up. Made easier, for the nonce, by me not having the money for them, after taking them for 35 years. I am totally NOT on the fence about eating a plant diet!

    This one may be more heartening. I learned to make some pretty good kombucha tea a few years ago. Mmm, cold, fizzy, tasty, they said it was good for me, what’s not to like? Especially when I am *not* one of those health food fanatics – there’s always one in every online board – who drink quarts of kombucha daily or, I sh*t you not, the broad on Marie Oser’s soy board who described her diet of soy this for breakfast, soy milk that, soy theotherthing for lunch, soy yogurt, soy this for dinner…. barf. Nut.

    But maybe I can relax and stop making it. Making it was waaay cheaper than the $4 (I sh*t you not) pints in the health food stores. [Spoken in a Dr. Greger voice] Not making it would be… even cheaper.

    Still makes one long for ca. 1967 Mad Magazine’s ideal business street. The health food store’s sign said: “We don’t overcharge for stuff just because it’s good for you!”

  • Matthew Cahn

    “Chunks of slimy fungus?” do your research, fungus is mycelium, kombucha has chunks of yeast.

    • I believe you are mistaken. Yeast are unicellular fungi. Kingdom fungi, phylum Ascomycota, class Saccharomycetes, order
      Saccharomycetales, then typically family Saccharomycetaceae.

      • Matthew Cahn

        Guess you’re right on that point. I still don’t think you’ve given a complete picture of the potential benefit’s / risks of Kombucha. There is a lot of other research out there yet you’ve only quoted ONE study. What about the high levels of antioxidants in Kombucha:
        Also the “Potential use of d-glucaric acid derivatives (found in Kombucha) in cancer prevention” :

        Also this paper quoted “Research conducted in Russia at the beginning of the century and testimony indicate that Kombucha can improve resistance against cancer, prevent cardiovascular diseases, promote digestive functions, stimulate the immune system, reduce inflammatory problems, and can have many other benefits.”

        I’m not saying that there aren’t health risks which is why proper standards are necessary to make sure Kombucha is prepared properly. Similar to Vodka, which can make you blind if it isn’t prepared properly.

        • Tom Morphew

          Thank You for the links to studies that lend to education of kombucha use & benefits

  • Lee

    A short while ago I saw a video presentation from NutritionFacts site that included a chart for fruits, vegetables and grains for acid vs alkaline content. I have been unable to find this in my search of the site. Can you please help me to locate it? Thank you.

  • Dianne Barnard

    I was very sorry to have missed your lecture at St. Clair Hospital. I was waitlisted but after viewing this little snippet, I am glad that I didn’t go. I feel that you have a responsibility as a doctor to present information in a meaningful way. This is prejudicial and presented in a cutesy tongue in cheek manner that is disappointing. I think that if you find this information to be possibly life saving, then you should present it in a way that people can understand and not in an alarmist way. Sorry, not a fan of this video. I am disappointed! This is important information, not a joke.

    • HereHere

      In some way, I agree with you. This video is not balanced, although I’m not a kombucha drinker. Scrolling down the comments, there are many studies that people have put forward. That said, I attended Dr. Greger’s lecture two years ago, and it was quite good. It certainly helped educate an audience of people diagnosed with various forms of cancer, and those supporting them.

  • Jerusha

    Comparing Kombucha with Raw Homemade Vinegar:

    I was wondering if this could cause a similar problem with making your own vinegar. I know from other nutritionfacts videos that vinegar is good for you. If I made my own vinegar, which uses a similar process as kombucha making, and even has a “mother/scoby” like the one in kombucha….would the vinegar have the same health risks as kombucha? Or is there something different with vinegar that causes it to be safe, even when making it at home?

  • Cynthia

    Love your site, admire you greatly, but one day you will ferment and then drink your kombucha conclusion. We can all prepare a food badly and get sick from it, but considering the thousands of years and millions of folks who drink kombucha, its benefits do outweigh the very small risk so far reported. At a minimum you could have just asked people to be careful as to how it is prepared. As to the rest of your site, I raise my kombucha glass to you!

  • Rosemary Guy

    Excerpt from above link:
    While an under-fermented probiotic may harbor pathogens or fail to develop the beneficial nutrients, an over-fermented probiotic (higher in acetic acid) may overburden the stomach’s digestive juices. Here’s why. The acidic pH aids the stomach’s digestive juices and helps break down food and relieve stagnation. Acetic Acid from Kombucha and Lactic Acid from kefir are all weak acids. When ingested, they react with minerals such as Calcium, Sodium, Potassium and Magnesium in the body tissue and blood, to form alkalies. This reaction is termed Alkaline-forming foods. That is how an acetic kombucha tea actually helps alkalize the body. However you have to be very careful in not over doing this. An excess will rob your body of ionic minerals. A cup or two is fine, but large amounts of these acids are not a good idea. How much is too much? It is a relative term. For a normal healthy adult the amount is thought to be 4-8 fluid ounces daily. (see Drug interactions). This amount appears to be comparable to another popular folk remedy – Apple-Cider Vinegar. The most often repeated recommended dosage for ACV is one spoonful daily. The reason is that typically ACV is 5 % acetic acid – almost 5 times that of Kombucha Tea. There are other differences but our focus here is on the acetic acid. Kombucha tea is far less leeching (a common AMA complaint) and kombucha, because it is alkaline forming, will not create acidosis in a healthy individual. If it does it is far more indicative of a deeper more serious disorder.

  • Derrek

    What are some natural sources of good bacteria? I flatulate a lot and probiotics can be expensive.

    • counterbond

      hate to tell you brother but probiotic foods will just make you “flatuate” more…. saurkraut, pickles, kimchi, but kombucha doesnt really do that too bad

      • Derrek

        I think I have dysbiosis and a problem with low levels of good bacteria. That’s why I think it will help.

        • Mr Farts

          Had a similar problem after being on antibiotics. On advice from a friend i went to the farmers market. I got the most “dirty” fruits and vegetables I could find. Basicly anything just pulled out of the ground. I brought them home and blended them up, unwashed of course. I had diarrhea for one day and since then I’ve been fine.

  • Cherry

    I also think it’s a bit much to label Kombucha as Harmful. Did the case study mention why THIS person had this reaction, and why not every single person who drinks Kombucha ends up in a coma?

  • Sally

    I do not hear evidence one way or the other in your “statement”

  • LDGourmet

    I wonder if there is more evidence you could share about ‘more harmful than helpful” for WHOM?

    I am finding kombucha helpful to my digestion. I drink water too, and hibiscus and green tea. But am I at risk for acidosis or toxicity? Isn’t kombucha just another fermented product we hear such good things about? I feel we need more info on this. Was that case review subject drinking homemade ‘booch? Gallon a day? Had pre-existing poor health?

    Is that case sufficient to stop drinking something I seem to find beneficial??

  • Drake

    Current evidence on physiological activity and expected health effects of kombucha fermented beverage:

    “It is shown that KT can efficiently act in health prophylaxis and recovery due to four main properties: detoxification, antioxidation, energizing potencies, and promotion of depressed immunity. The recent experimental studies on the consumption of KT suggest that it is suitable for prevention against broad-spectrum metabolic and infective disorders. This makes KT attractive as a fermented functional beverage for health prophylaxis.”

    Effect of Kombucha, a fermented black tea in attenuating oxidative stress mediated tissue damage in alloxan induced diabetic rats.:
    Hypoglycemic and antilipidemic properties of kombucha tea in alloxan-induced diabetic rats.


    The findings revealed that kombucha tea administration induced attractive curative effects on diabetic rats, particularly in terms of liver-kidney functions. Kombucha tea can, therefore, be considered as a potential strong candidate for future application as a functional supplement for the treatment and prevention of diabetes.”

    • Joseph Gonzales R.D.

      Thanks for sharing. We’ll look into the studies you so nicely listed and update the information on Kombucha as necessary. One question though to your studies, have you found any conducted on humans? Looks like all of these were conducted on mice or in a petri dish. Human trials are the gold standard! Stay tuned for more on Kombucha. I appreciate your comments.

  • Jill

    Never believe what you read in a health food store?, that might have been true 30 years ago ( maybe) but how can you make such a blanket statement now, maybe we are supposed to believe the big PHARMA companies, tha t makes more sense, we should be getting away from the stigma of “hippy” health food stores” not being scientifically sound, the FDA sure knows better, not. You are taking us back 50 years by that comment. Also, while I’m on my soapbox, kombucha tea could be harmful, but so can other substances that could be contaminated, not just because of it being kombucha. From other comments, you are an objective person but from this article you are definitely close minded and someone I would NEVER look to for advice, you are just trying to give something that can be beneficial a bad name because someone obviously got a bad batch ( kind of the same thing that happened to L-tryptophan when it was banned and bastardized for years because there was one bad batch that was contaminated. And how about those sprouts that were contaminated, do you recommend people Never eat SPROUT, because of a bad batch! Stop trying to shock the public and scare them, it’s unbecoming and unnecessary, positive comments are much more helpful. I just realized this was dr. Gregor, VERY disappointed, I’ve heard you speak and thought highly of you at the time, but to make the comments you did based on a few cases is WRONG. Hope you take heed from us and stick to what you KNOW to be true, a plant based diet is beneficial and can be life changing, but to hear you make these comments is VERY disconcerting.

    • Joseph Gonzales R.D.

      Hi Jill. Thanks for your comment. We’ll update the research on kombucha as more is available. I think the reason why Dr. Greger reported on this case study was for those who drinks tons of kombucha this may warrant caution. I agree that so many foods could be contaminated and perhaps a kombucha every now and then is not the worst thing to consume, nonetheless, Dr. Greger felt the need to report on it.

      • jj

        Then that is how Dr. G should have worded his warning …” for those who drinks tons of kombucha this may warrant caution.” He didn’t say anything about dose just … “Consumption of this tea should be discouraged” as if any at all would be harmful.

        • Daz

          Good point.

      • Daz

        Good point, plus he says that vinegar is good… or at least two tsp a day… kombucha becomes vinegar… it is often recommended people drink adequate amounts of water if drinking kombucha…. cheers, a lot of positives cited by way of gut benefits, immune system, digestion, b vitamins…. also agree, pls look into water kefir…. thnx

  • will you look into kefir? Is there a good site that you would recommend in learning how to effectively read research? I know that a lot of learning goes into the concepts presented, but it would be nice to have some idea as to how to navigate them to even find what to look up and define. Thanks for the empowerment, Doc!

  • Jane Buscemi

    Kombucha, ok I’ve been brewing my own with Pu-erg yellow tea, after reading this piece, it sounds like I should have my tea analyzed! In looking at the article you based this clip on and doing a new search, it seems like there is more out there now! Care to take a second look? I am not immune compromised and having trouble with the concept of giving up my Kombucha tea!

  • Tom Morphew

    sarcastic , nonfactual , insulting to my intelligence . Have heard much boasting of Dr. Greger I would hope this to not be representative of your contributions “complete with bits of slimy fungus” like the mother in vinegar? “live a measly 2000 years” lacing the lack of fact with sarcastic attacks on chinese folklore from a couple of millennia past not to mention what was lost in translation….Yes I am unimpressed . I would welcome a contact to have my Kombucha tested at a reasonable cost . I don’t advocate drinking it like sodas good sense & moderation being the key to most if not all things in life , I am sure there are persons allergic or intolerant . Anyone who would care to partake should start with a ounce before a meal , not guzzling a 16 ozer on a empty stomach for refreshment on a hot day! Treat your body as your temple love , kindness , gently nourished , respected & protected

  • Julie

    I find this so amusing after seeing that the video was put out by an MD and the article that was written were both by MD’s. This all makes sense to me now.

  • ciphersimian

    I would like to see some updated information on kombucha with respect to its probiotic and antioxidant properties. I’m genuinely curious if the case of lactic acidosis mentioned in the study was from improperly prepared kombucha. I would also like to see more information on fermented foods in general and some recommendations on what foods we SHOULD be eating to get probiotics on a vegan diet. Thanks!

  • FloridaBoyee

    I have a problem with gran mol seizures and am on medication for this. Is this alright to drink? Thank you.

  • Charma1ne

    I do like the taste of Kombucha and it helps with my craving for fizzy drinks. This article sent me to my fridge to have another look at the kombucha labels. I made the assumption, based on what I have read that Kombucha contains probiotics but alas the type I use does not. What it does contain is green tea, a live scoby and 5.3 grams of sugar per 100 millilitres. Nowhere on the bottle does it say that my excellent tasting drink contains probiotics or will in any way benefit anything but my tastebuds. Apparently, according to Summer Bock, the fermentationist, the sugar added initially used in the brew remains in the drink although the molecule is broken apart.

  • Casey

    Hi Dr. Greger! As I greatly respect your knowledge and authority, I hope to hear more about Kombucha from you. I think it definitely deserves some looking into. It seems it should have the reverse effect and would alkalize the body rather than make it more acidic. Here is the CDC report on the case you mentioned.

    • payoung

      Hi Casey, the study cited in this video was a case of a 22 y/o male who had been recently diagnosed HIV positive. He was found to have lactic acidosis after drinking Kombucha tea. The CDC cases you linked were of women in there 40’s and 50’s. In any case there have clearly been cases of adverse affects after drinking Kombucha. As far as the question of why acidosis…Kombucha is fermented in much the same was that vinegar is which is also acidic. While vinegar contain aectic acid Kombucha contains acetic as well as other acids such as gluconic acid which are all produced in the fermentation process.

  • Zurd

    There’s been new studies published since this 2010 video. It would be interesting for nutritionfacts to analyze them and make a new video since Kombucha has never been as popular as today. Reference:

  • Heather Guidi