Is Kombucha Safe?

We love to ferment things, with one notable exception: kombucha. During the last kombucha craze, in the mid-90s, we picked up a “SCOBY” blob and dutifully fed it tea and sugar until we stumbled upon an article written by mycologist Paul Stamets, “The Manchurian Mushroom: My Adventures with “The Blob.” In that article Stamets tells a convoluted story of having a kombucha culture tested by a lab. He didn’t tell the lab what it was.The lab was very excited about the results on this mystery substance, and Stamets soon finds himself “sitting in a board room of a pharmaceutical company with lawyers and contracts discussing the particulars of patents, sub-licensing agreements, market territories, and dollars running into the millions—if FDA approval was granted for a novel drug.

Then the folks in the meeting turn to Stamets and ask him to reveal the identity of this culture:

I told them that, as best as we had been able to determine, from analyses by several independent mycologists, that the Blob was a polyculture of at least two yeasts and two bacteria, living synergistically.

The silence was deafening.

“Say what?”

Perplexed looks crossed their faces, soon followed by exasperated expressions of deep disappointment. Which of the organisms are producing the potentially novel antibiotic? Was it one or several? Was it one in response to the presence of another organism? Was it one in response to several organisms? The sheer numbers of permutations would complicate trials and given the FDA’s disposition, a polyculture is de facto contaminated.

The meeting was abruptly adjourned.

So kombucha does indeed have medicinal properties–including “novel antibiotic” properties– but therein lies the problem. Stamets concudes,

Those who might benefit from Kombucha need a credible and experienced professional who could best prescribe and administer it. I do not see the advantage of taking Kombucha by people in good health. Given the detrimental effects seen from prolonged exposure to antibiotics, the repeated, long term use of Kombucha may cause its own universe of problems. I wonder about those people who have adverse reactions to antibiotics? What about those with sensitivity to the microorganisms in Kombucha? I personally believe it is morally reprehensible to pass on this colony to sick or healthy friends when, to date, so little is known about its proper use. At present there are no credible, recent studies as to the safety or usefulness of Kombucha, despite decades of hype.

Stamets also expreses concern over contamination. A German study found three out of 32 samples of kombucha cultures taken from German households to be contaminated with Penicillium spp. and Candida albicans. While describing the contamination rate as “low” (nearly 1 out of 10 samples seems high to us) it goes on to recommended that immunosuppresed individuals buy commercial kombucha instead of making it at home. A literature review conducted by the Universities of Exeter and Plymouth in the UK concludes, “the largely undetermined benefits do not outweigh the documented risks of kombucha,” said risks including, “suspected liver damage, metabolic acidosis and cutaneous anthrax infections.”

We’re all for fermented foods, and support the home fermentation of classic pro-biotics like yogurt, sourdough and lacto fermented vegetables. The last thing we want is for people to get spooked away from home fermentation. But kombucha is different. The problem, as Stamets notes, is that kombucha’s sugar and tea medium is a kind of open house for cultures, some good, some bad. Yogurt, sourdough and salt brines are very selective mediums in which to ferment things. With komucha it’s much more of a crap shoot.

Basically, like Stamets, we’re intrigued with the notion of kombucha being tested as a medicine and used with care by both western medical types as well as herbalists. And even if we were guaranteed a pure culture and a solid methodology for keeping the culture uncontaminated, we’d still be too leery its antibiotic properties to consider it a casual beverage. So we just don’t do the kombucha thing.

Leave a comment


  1. Interesting. I haven’t tried any Kombucha, but have been curious about it.

    Glad to know that I don’t need to bother trying it.

    So thank you!

  2. If Stamets has serious reservations about kombucha and is saying so publicly, I consider that sufficient reason to steer clear of it for casual consumption, as you say. Stamets is deeply knowledgeable on all things mycological, so I would heed his cautions.

  3. Hi Kate,

    Kombucha is not a mushroom. So Mr. Stamet’s expertise doesn’t actually apply here. Not to say he is not a reliable source, but on this topic he is simply repeating what he is told, not offering true expertise.


  4. Kate, Hannah:

    Kombucha is a symbiotic organism which is part yeast, and yeast is fungus–yeast, mold and mushrooms all hail from the kingdom of Fungi. (Penicillin is also a fungus.) What’s interesting about kombucha it seems that no one knows exactly how it works. I’d very much like to hear from a true kombucha expert–if one exists. In the meanwhile, Stamets isn’t a bad source, imho. He knows more than I do about fungi.

  5. Hi Mrs Homegrown,

    Kombucha experts? Sure:

    Michael Roussin: He conducted research on over 1100 homebrews and found a whole host of great stuff in Kombucha. He also debunked that silly FDA warning. He published the FDA’s own documents saying they never tested any Kombucha.

    Ed Kasper: The Happy Herbalist, he’s done a number of Kombucha experiments, highly recommends the use of kombucha.

    Gaia Research New Zealand: A great synthesis of all the Kombucha research done over the last 100 years. Especially valuable is the collection of research done since 2000.

    A quick Google search of these folks with “kombucha” will turn up a ton of results. The info is out there! 🙂


  6. Hi Again Mrs Homegrown,

    As to your question for how Kombucha works, that much is very simple. Kombucha delivers digestive and blood balancing acids and enzymes that improve the function of the eliminative systems. Meanwhile, probiotics (in un-pasteurized kombucha) repopulate the gut with healthy bacteria.

    Kombucha does not cure anything!
    It is not a panacea!

    It simply helps the body operate more efficiently, which gives the body more energy to do everything else. It is not magic, it is just part of a healthy lifestyle that aids in balancing the anti-biotic world we are living in.

    I hope this helps! 🙂 Please feel free to ask anything else, if I can help I will!


  7. I read Stamets’s article, and have a lot of respect for him and his work. I did snag on the concept of a polyculture.

    The sourdoughs and kefirs that we work with are all polycultures – mixtures of yeasts and bacterias – usually many. Sourdough, for instance, is lactobacillus and any number of various yeasts.

    When he says a polyculture is de facto contaminated, what does he mean by “contaminated”? Is he referring to the fermentation that most people would take for “rot”?

    Water kefir grows on sugar water, as well. Doesn’t wine? Mead? Yet I have not read of dangers concerning these.

    My thought is that these cultures have been around for hundreds of years and provided benefits to the societies that used them. Moderation and careful cleanliness are probably key to keeping them safe. But, honestly, I do not know for sure.

  8. I was faithfully fermenting and drinking kombucha for several months last year when I noticed a gradual achiness throughout my muscles. My husband said I was “walking like a little old lady” because I was so stiff and sore. When I stopped drinking the kombucha daily it went away. I believe I was suffering from ingesting too much lactic acid, a major component in kombucha. These days I buy a bottle occasionally, but no longer drink it on a regular basis, and I have stopped making it myself. And I feel great.

    Bottom line — it my be healthy for some people, but it’s not for everyone.

    • There are a few reported cases of illness or even death that may be associated with kombucha. But they are by no means proved and would never have been published if say a few people took “X” and it cured their cancer. The denominator on the other hand is huge – millions, tens of millions? So the risk would be minuscule. Medicines are much better studied and all have some nasty side effects.

      In short, I think the risk is very small but no guaranties.

      By the way, the liver naturally breaks down lactic acid. Our muscles make it all the time.

    • Since posting this I had a chance to talk to Sandor Katz. His take was that Stamets is overreacting that, as a mycologist, Stamets is not comfortable with symbiotic, unidentifiable cultures. Katz added that he thought drinking kombucha regularly may not be so healthy due to the sugar content. Once in awhile, ok, but not all the time. I’ve since come to agree with this more moderate viewpoint.

  9. Hannah:

    Thanks for those resources–we’ll look into them as we have a chance. We’re super busy the next few days, so I can’t look at them right now.

    What I’m primarily concerned with is Stamets’ lab findings that kombucha has novel antibiotic properties.

    To my mind, that makes it a fascinating candidate for alternative medicine, but not so cool for regular use by healthy people. If I find information that refutes those findings, I will reconsider.

    Other, lesser, things that bother me include the fact that no one can date its existence prior to 100 years ago or so. Most human ferments are ancient, ancient, ancient. It seems to be a new culture, one which feeds on a specifically modern medium of tea and sugar. Is it a product of our modern habits?

    Back in the 90’s when we last kept one, I got tired of shoveling sugar at it. It struck me as a junk food addict. This sounds flippant, but I don’t mean to be. Cultures have personalities–vibes, sort of– and my gut just tells me this isn’t a guest I want to keep in my home. That’s a very personal response, so it didn’t go in our post.

    All that said, I do know that many people love kombucha and believe it has improved their lives, and I do not deny the validity of their claims. I’m just saying that it’s for us.


    I don’t believe Stamets himself is bagging on polycultures–it’s the FDA that perceives them as de facto contaminated. They’re too irregular for research, I guess.

  10. Hi Mrs Homegrown,

    Thanks for your reply. I am pleased to find your stated attitude towards Kombucha very different than the one expressed in the article. I fear that your readers may have come away with not only a misimpression of Kombucha, but seemingly a misimpression of your own views on the subject.

    I would never suggest that someone who did not enjoy consuming Kombucha continue to do so. Just like all foods, our body’s chemistry tells us if it is a good fit for us, and there are other options for fermented foods, though I find Kombucha to be one of the easiest most versitile for daily consumption, plus it seems to have the greatest variety of good stuff in it from what I’ve read.

    Just to be clear: there are no proven/linked cases of Kombucha toxicity on record in the United States. There have been 2 suspected/alleged, but with no actual evidence, just conjecture. Neither case repeated itself, and one of the two alleged cases involved store bought tea, so homebrewing wasn’t even an issue.

    Folks like Diane who find it’s not for them should absolutely find another option. But to imply that Kombucha presents real health risks broader than most home food preparation is not supported by anything I have found.

    As for the “ancientness” of Kombucha, Ruth famously partakes of a “vinegary beverage” in the Old Testament, and there are historical writings about a vinegar beverage being carried in the flasks of Genghis Khan’s army as well as ancient Japanese warriors, sort of a first “energy drink” that fermented as they carried it into battle. Tea beverages and fermentation have been around forever.

    As for the sugar that goes into Kombucha, according to Michael Roussin’s research, properly brewed Kombucha contains less sugar than a glass of fruit juice, and one can increase the length of the brewing cycle to bring that down further if desired. The fermentation needs fuel, but the sugar was never for you! 🙂

    Thanks for the opportunity to weigh in. I enjoy the discussion.

    Peace and Love,


  11. Teresa

    As someone who makes their own yogurt and beer much has to be said about the conditions in which a microorganism is allowed to grow. For instance with yogurt the pH rapidly becomes acidic which prevents most bacteria especially pathogens from growing. It is also seeded with a relatively pure starter (commercial yogurt) and when used through multiple batches starts to produce a more harsh flavor.
    In the case of mead or wine you can get some pretty foul concoctions if you don’t practice pretty careful hygiene. Again, not very likely to be pathogenic but the smell???? There is reason beer and wine use specialized yeast instead of a readily available variant typical of bakers.

  12. Great article. I made my own kombucha for a few months but decided to stop because I also didn’t like “shoveling sugar” at it. I’d rather bake sourdough now. Occasionally I will buy a bottle if I feel tired or have a digestive issue, and I do feel generally refreshed when I drink it, but I’m not such a fan that I want it to be a part of my lifestyle.

    I hope you don’t mind if I link this post to my blog? I have noticed many people searching “kombucha” in Google have landed on my site, and I’d love to add this article to that page and spread the word.

  13. A Case of Kombucha Tea Toxicity
    Journal of Intensive Case Medicine Vol 24 No 3
    May-June 2009 205-207


    Introduction: Kombucha “mushroom” tea is touted to have medicinal properties. Here, we present a case of hyperthermia, lactic acidosis, and acute renal failure within 15 hours of Kombucha tea ingestion. Case Presentation: A 22 year old male, newly diagnosed with HIV, became short of breath and febrile to 103.0F, within twelve hours of Kombucha tea ingestion. He subsequently became combative and confused, requiring sedation and intubation for airway control. Laboratories revealed a lactate of 12.9 mmol/L, and serum creatinine of 2.1 mg/dL. Discussion: Kombucha tea is black tea fermented in a yeast-bacteria medium. Several case reports exist of serious, and sometimes fatal, hepatic dysfunction and lactic acidosis within close proximity to ingestion. Conclusion: While Kombucha tea is considered a healthy elixir, the limited evidence currently available raises considerable concern that it may pose serious health risks. Consumption of this tea should be discouraged, as it may be associated with life-threatening lactic acidosis.

  14. Thanks for the lively discussion on kombucha – a refreshing change from the usual uncritical comments found elsewhere. Fermented foods are generally healthy – some of our most valuable foods are fermented and the fermentation process produces many healthy byproducts. It is an interesting question regarding the age of the culture – its true that refined sugar is a modern product and no one seems to suggest that honey or fruit juice was used in past centuries, although that is possible. That being said yeast have no problem with refined sugar and it is not a ‘junk’ food for them as it is for us.
    Much of what is written about kombucha is hype or outright false. One of the most common claims for kombucha is that it contains probiotic yeast and bacteria – organisms that help with digestion and other functions by living in the intestines. This claim is false. The yeast and bacteria that are used to make kombucha are not the same as those found in yogurt or other cultured milk products. Nearly all manufacturers claim that kombucha must be kept ‘raw’ so as not to kill healthy bacteria, but this only results in continued alcohol production. Probiotics, like almost all microbes, cannot survive in the acidic conditions of kombucha.
    One company that is trying to be honest and truthful about kombucha is Kombucha Wonder Drink. More information about what kombucha really is can be found on their website at

  15. I also used to brew Kombucha, it was one of the first home fermentations I ever tried when in college. I stopped brewing before I read the Stamet’s article because I started feeling slightly suspicious about it.

    Reading the Stamet’s article, even though it was outdated, put the final nail in the kombucha coffin for me!

    Thanks for bringing this topic up.


  16. Thanks for the great info presented here, especially in the comments section!

    A big thanks to Hannah for defending the ‘booch! I did also get the impression from the article that kombucha was dangerous, and if I hadn’t been drinking it for the past 3 years I probably wouldn’t have started drinking it. so it is good to see various opinions offered in the comments here!

    As people mention everyone has a different experience, I do find with kombucha that you should start with small amounts, but that is a good rule of thumb in general.

    I have had serious digestive problems as I got typhoid in Burma and have had a not very good liver for years since I got hepatitis A in PNG when I was a kid–since drinking kombucha my liver has really improved it’s ability to detox. It used to be if I drank one beer I would be puking ill the next day and unable to eat or drink anything. Now I can actually have a couple social drinks once in a while and be fine the next day. I’m not a big drinker but it is nice to be social. My digestive condition has also improved remarkably.

    I do warn people when passing on SCOBY’s to be careful when they start drinking it and to be aware that kombucha could be the cause if they start feeling strange. It is good to get a plethera of fermented foods–as of course our digestive tracts like diversity better than mono-cultures like most everything else in our world. Good to know your own body and trust your own experience and feelings about a fermented food–as mentioned above different folks have affinity for different micro-organisms.

    Personally I have been trying to learn how to communicate with my gut flora, to try to find out directly from them what they really like–heh…

  17. I wouldn’t have flown with Wilbur or Orville because of the danger then. Now airplanes are totally accepted even though sometimes they crash and kill people.

    I am going to keep making my gallon per week of kombucha using the continuous process and enjoying it after aging with the fruit juice (cranberry-pomegranate) I add to it.

    Chicken-Little, the sky is not falling in, IMHO.


    • A 2003 review of clinical studies of kombucha, that you can access here:, states:

      “Kombucha has become a popular complementary remedy. The aim of this systematic review was to critically evaluate the evidence related to its efficacy and safety. Methods: Computerised literature searches were carried out to locate all human medical investigations of kombucha regardless of study design. Data were extracted and validated by the present author and are reported in narrative form. Results: No clinical studies were found relating to the efficacy of this remedy. Several case reports and case series raise doubts about the safety of kombucha. They include suspected liver damage, metabolic acidosis and cutaneous anthrax infections. One fatality is on record. Conclusions: On the basis of these data it was concluded that the largely undetermined benefits do not outweigh the documented risks of kombucha. It can therefore not be recommended for therapeutic use.”

      Sorry to say it still seems like a dodgy fermentation project to me.

  18. seriously brother.. you have no facts and are basing this off of “personal belife” as you said and speculation.. has anybody actually read facvtual obaservations by people who really reaserch these things.. well by the way you expliain your arguments it sounds like a bunch of rednecks sitting aroubd a table saying i dont belive…. there is nothing actually factual about this and for stammits and how he represnts things like a god to certain people.. yall should base it off of facts and not personal belifes

  19. There is no comparison between a substance such as Kombucha and its natural antibiotic action and that of man produced antibiotics. Garlic is a natural antibiotic but you cannot build up immunity to it like a chemical antibiotic. This way of thinking is simplistic and reductionistic and has absolutely no basis in reality.

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  21. Thanks for this article. I’m an experienced homebrewer and lacto-fermenter, and recently (finally) acquired a scoby from a friend.

    As far as kombucha toxicity goes, I’ve only found the actual case studies for three hospitalizations (two in Iowa in 1995, which were linked and which was fatal to one, and the 2009 case described in the comments above.) So, three serious cases of harm in 18 years.

    That’s not the worst safety record I’ve ever heard. Caffeine, another chemical I use daily, sends thousands of people annually to the hospital with things like palpitations, panic attacks, and more. A handful of deaths are linked to it, usually from synergistic reactions to other chemicals.

    Alcohol, a chemical I make at home and consume quite happily, kills and injures many every year, and in truth, every weekend.

    I raise these points only to note that the dangers of kombucha appear to be overstated – as frankly, I suspect the health benefits are as well. But I like the taste of kombucha, and I’m enjoying, for now, the process of making it at home.

  22. It sounds like someone who is repulsed by the way the scoby looks, but trying not to fess up to it but trying so incredibly to sound scientific about it. Love his words to defame it like “suspected” liver damage. Ha ha ha. I suspected the moon was cheese once.
    This man will probably not live as long as he could. In Russia, if you are in a military hospital they administer a liter per day of Kombucha to help detox you. I used to think what diabetics were the only drinkers of the stuff. My health is way way good and energetic. John
    ps because of the monster pharmaceutical beast and the way the FDA are in cahoots, it will probably never get a thumbs up from the FDA. As if I really cared what they say anyway.

  23. I have recently acquired a SCOBY from a friend and currently making my third batch. I am pre diabetic and trying to lower my blood sugar without the use of drugs. After only drinking it for a couple of days (a cup a day), I immediately noticed that my morning fasting readings are significantly lower, and lower than it has been in a long time…even after eating a half bag of candy the night before. I have been measuring for a week and can say that it’s the kombucha. Not only does it work for me, but I also enjoy the refreshing sweet/tart flavour. I am going to continue for a month, being careful of diet (no more M&M’s!) record my daily food intake, and see if I can get my glucose level in an acceptable range. BTW, I normally watch my sugar intake and the readings never budged, the kombucha is the only thing that has made an instant change!

  24. I first tried kombucha in the mid 90s. One effect was a chronic point of pain from a auto collision completely disappearing with in minutes after the first 2 ounces. I was give a “SCOBY” from that mix and kept brewing and using it until I moved from that area.
    Since then I have tried other kombuchas and have not found the same taste or well being feeling from the first use. It is not at all close to the same “strength” if that would be the proper term here. The first efforts were such that consuming more than 2 ounces at a time was never a serious consideration. Now friend that use it are drinking glassfuls through out the day. I found this site hoping to find a plausible explanation of my experience and I think I have. With the variable’s that go into the making I would guess some super strains, good or bad, come about. Finding or creating the ones that offer a greater or reduced benefit or course of action seems to have become something the general public will never hear about yet has been incorporated in mass production.

    • Mr. Lee,

      I believe you are referring to something that very few people seem to have caught onto, namely, that these organisms go dormant after being in cool temperatures. The longer they are dormant, the longer it takes to wake them up. Dormant organisms take a long time before they are in reproduction mode. Homebrewed Komb and buttermilk are vastly more powerful than storebought because the organisms are either active OR they are not too far away from being active. THEY ARE PROPOGATING IN YOUR DIGESTIVE TRACT! I make buttermilk every 3 days and you can’t imagine how much better and more powerful it is than storebought.

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