Kombucha: A symbiotic mix of yeast, bacteria and the naturalistic fallacy

06Jun13
Feeling thirsty?

Feeling thirsty?

If you grew up in the seventies, you may remember the same food fads as I do. There was the oat bran buzz that was replaced by the wheat germ movement, the family fondue set and the homemade yogurt maker. And for a while I remember my father making what I called “aquarium water” – a foul-looking jug sitting on the kitchen counter with a gelatinous white mass floating on top. Despite the assurances it was good for me, I declined the taste tests. They didn’t push it and I never volunteered to drink this “cure all”. I thought kombucha had gone the way of gelatin-based salads and entrees, until a friend told me she was drinking it. Not only is it still a home-brew darling, kombucha isn’t just for hippies: There’s probably some for sale at your local organic grocery. Yet after a bit of digging, kombucha culture still seems mired in the 1970′s. It’s still touted as a panacea, and it’s still one of the more questionable folk remedies out there.

I understand the intrinsic appeal of the folk remedy. In an era where we can buy everything we possibly need, there’s something meaningful and satisfying about making your own food from scratch. I prefer bread, particularly sourdough – but I’m not making any health claims. Like food recipes, some home remedies are handed down from generation to generation, or passed on by word-of mouth. The attractiveness is both an appeal to antiquity combined with pattern-seeking and anecdotes. We remember the “hits” of those home remedies but not the misses. And we never test causality. Is it possible that kombucha could have medicinal effects? Sure. Beer and wine didn’t come out of a medicinal chemistry laboratory either – and look how helpful those fermented products are. As a fan of beer, cheese, sauerkraut, and yogurt, I’m strongly pro-fermentation. So while we can’t make Tylenol in our bathtub, or grow our own antibiotics, how about an odd-flavoured tea-based beverage filled with the magical healing properties of yeast and bacteria? I’m told it’s all about the microbiome, so perhaps they were on to something in the 1970s. Authentic and artisanal is where it’s at today, and what could be more artisanal than home fermentation of a remedy?

As with most folk remedies there are multiple claims for kombucha’s ancestry, from the Ukraine to Asia, from “millennia ago” to a few hundred years ago. However or whenever it occurred, the recipe is similar. Kombucha is sweetened black tea fermented by a mixture of yeasts and bacteria that form what looks like a “mat” on the surface. Sometimes called a symbiotic colony of bacteria and yeast (SCOBY), the “mushroom” or simply the “mother”, this “zoogleal mat” ferments the sugar, producing alcohol, vinegar, and other by-products. To get started, you need to obtain a starter mat – you can order them online, or ask someone that already grows their own. The result of fermenting on your counter is exactly what I remember growing in our kitchen, though it actually looks more brackish than I remember. After fermentation it’s lightly carbonated. Taste reports of kombucha vary from “refreshing apple cider” to “vomit”.

Like other folk remedies, kombucha’s efficacy is apparently legion. HIV, aging, hair growth, gout, diabetes, hemorrhoids, memory loss, PMS, cancer, hypertension, and the perennial “boosting” the immune system are no match for the healing and restorative power of kombucha.

What is that growing on and in my drink?

Several researchers have examined the bacteria and yeast in the kombucha mat. Content can vary considerably, based on the geography, climate, and local bacteria and yeasts. Bacteria include Bacterium xylinum, Bacterium gluconium, Acetobacter hetogenum, Pichia fermentons. Sometime antibiotic-producing bacteria like Penicillium species can be detected. And then there’s the toxic bacteria that has been detected, such as Bacillus anthracis – anthrax. Yeasts include Schizosaccharomyces pombe, Torulaspora delbrueckii and Zygosaccharomyces bailii. Contamination with Aspergillus fungus has also been reported, as well as Candida. Yes, that fungus that’s poisoning us all (according to alternative medicine proponents). Various Candida species including C. albicans, C. kefyr, and C. krusei are also found in kombucha.

The final ingredients vary with the bacteria and yeast in the mat, as well as the extent to which fermentation has taken place. Analyses have identified small amounts of alcohol (usually under 0.5%), substantial acetic acid (vinegar), ethyl acetate, glucoronic acid, and lactic acid. There’s some residual sugar, depending on how long it’s been fermenting. Caffeine is still present and may be responsible for some of the energy claims. It’s claimed to contain B vitamins, though I could locate no reliable source to confirms this.

The kombucha "mother"

The kombucha “mother”

The evidence

Despite the hundreds of thousands of posts on kombucha praising its medicinal and health effects, I was unable to identify a single clinical trial for any specific use. There’s a systematic review by Edzard Ernst dating to 2003 that also failed to find any clinical trials or even case series that suggest kombucha has medically beneficial uses. So there is no evidence to demonstrate or even hint at efficacy. Based on what’s known about the active ingredients, there’s no reason to expect it would offer any medicinal effects other than the consequence of low levels of alcohol or caffeine.

The toxicity

Given this is usually a home-brew concoction, there is the significant risk of contamination. In contrast to the lack of benefit, there is good documentation of the potential for harms associated with kombucha:

  • an alcoholic developed jaundice after two weeks, which resolved after discontinuation
  • dizziness, nausea and vomiting that resolved with discontinuation and restarted with rechallenge
  • toxic hepatitis that resolved with discontinuation
  • metabolic acidosis and disseminated intravascular coagulopathy, resulting in subsequent cardiac arrest and death
  • metabolic acidosis, cardiac arrest (with recovery)
  • anthrax infections of the skin through topical application of kombucha
  • lactic acidosis and acute renal failure
  • lead poisoning secondary to making it in a ceramic pot

Given the potential for kombucha to grow potentially dangerous pathogens, it’s particularly important for those with compromised immune systems to avoid the product. Given the risks, pregnant or lactating women should avoid kombucha as well.

Kombucha sells out

Kombucha isn’t limited to the home brewer anymore, there are several commercial suppliers such as Synergy (touted by Dr. Oz, of course) and the requisite story of the breast cancer survivor who credits kombucha for her health (but not the chemo and radiation she also accepted). The claims come fast and furious: the fermented liquid heals all and cures all – digestion, immune system “boosting”, amino acids that “detoxify”. You can now find it combined with different juices and flavors, for those that don’t like the taste of the original. The recipes are the same, and the final products are not pasteurized, a situation that caused products to be pulled in the United States until producers found ways to stop the alcohol from exceeding 0.5%.

The bottom line

The best that can be said about kombucha is that it probably won’t kill you. There are no documented health benefits, so unless you really like the taste, there’s no clear reason to consume it. As I have written before, health decisions should be based on an evaluation of the risks and benefits. In the case of kombucha, the benefits, other than the subjective, are unsubstantiated. The risks are real, but also rare. So if that bet still looks attractive, kombucha may be for you. To each his own fermentation. As for me, I’ll stick with my own favourite fermentations: IPA and wheat beer, and pass on the moonshine panacea.

Photo from flickr user parkerthompson and flickr user Jasonunbound used under a CC licence.

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7 Responses to “Kombucha: A symbiotic mix of yeast, bacteria and the naturalistic fallacy”

  1. This stuff scares me (and not just because I’m pregnant). Just because it’s “natural” doesn’t mean it’s safe!

    • 2 Jacquelyn Tobin

      Poison Ivy is natural too but I won’t knowingly ingest it!

  2. I resent the illogical implication of this article that there is no benefit just because you know of none scientifically documented. Just because there hasn’t been peer-approved research on home-brewed kombucha consumption in humans does not mean health benefits do not exist. And for what it’s worth, preliminary studies in animals have shown gastrointestinal and immunological benefit. If there were funding for research (industrial R&D incentive), as there is for commercially designed probiotic strains, perhaps we would see the scores of anecdotal experiences validated in the mainstream scientific sphere.

    As health is an individual experience, and all bodies are different, I personally find that sort of anecdotal evidence very compelling, and I think it’s an unfortunate omission that in an article about kombucha and its supposed benefit, you summed up the entire history of its use as a health benefit with a dismissive label of “naturalistic fallacy” rather than writing a more balanced account of what evidence does exist to the contrary of your assumptions.

    • 4 Discoowl

      lol at anecdotal evidence being ‘compelling’ – this is the difference between belief and knowledge, that latter being based on something more than ‘it makes me feel good’.

    • The scientific method is how we determine what is real and what is not real. There is no other way do arrive at the truth, it is the best method we have arrived at over centuries of effort. Anecdotal experiences are useless for the reasons you stated in your second paragraph, all bodies are different. Until it is subjected to the scientific method, it will remain what it is, a naturalistic fallacy.

  3. “Sometime antibiotic-producing bacteria like Penicillium species can be detected.” Since when is the genus Penicillium considered bacteria?

  4. Hi! Great article. We just posted this on our FB wall. However, it was pointed out that Penicillium is not a bacterium – it’s a fungus. Also, by “Bacterium xylinum” and “Bacterium gluconium”, do you mean “Acetobacter xylinum” and “[something else] gluconium”? Because “Bacterium” doesn’t appear to be a genus. Cheers.


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