What is it?

Some people love it and some people hate it, but regardless, kombucha is here in Kiwi-land (New Zealand) as one of the latest health-drink arrivals. That’s not to say it’s new though. Kombucha is a slightly fizzy fermented tea beverage thought to have its historical roots[1] in China around 220 BCE. Often prepared and fermented at home it is now also commonly found alongside many other artisan beverages in up-market cafes and supermarkets.

Figure 1: Homemade kombucha with microbial culture (“mother”). Source: Kombucha 101 (left). Commercial kombucha product. Source: Eat Well NZ (right).

There’s no end of wellness blogs offering up the benefits and commentary about the drink and a surprising bounty of scientific literature exists. I’ve definitely bitten off an ambitious topic for my first blog post, with tonnes more information on health claims, biology, and research than I’d have imagined, but I hope I’ve achieved a novel  and entertaining combination of useful info.

What’s it taste like?

Honestly (and subjectively), just awful; like disappointment cider. That’s my impression anyway. Lots of people love the taste, and I suspect some are just putting up with it for its claimed health benefits – not unlike so many other superfood tonics. All-in-all it wasn’t really my ‘cup of fermented tea’. I got the chance to sample quite a myriad of different commercial varieties recently at the wonderful Auckland Food Festival. There’s a huge range of different fruity and ice-tea flavours on offer, most of which are probably a lot sweeter than home-preparations. General impressions were that of either soured fruit juice or bad cider – which I suppose is exactly what you’d expect from something that is essentially tea- vinegar. But, as I said, some people love it, and you really do have to live-and-let-live when it comes to tastes in fermented foods (think: sauerkraut, kimchi, and blue cheese).

Health Claims

Nothing short of having your own private Genie, the health claims range from the unsurprising superfood daily to-do list down to the downright magical.

Wellness websites and blogs cover off most of the everyday superfood benefits claiming that the drink aids in liver detox, increased energy and immunity, improves mood and libido, looks after your joints, may help with weight loss but prevent hair loss, and that is also acts as an antioxidant (but then apparently, what doesn’t these days).[2] And this is hardly an exhaustive list – it’s a busy little soda. Commercial products also often boast about the presence of active probiotics (live beneficial bacteria) on their labels which are suggested to improve gut health and aid in digestion.[3]

But wait, “there’s more!”. There are also more extreme claims such as stories of regular use curing and pushing cancer into full remission,[3] the treatment of HIV/AIDS, reversing heart disease, and ridding you of diabetes.[4]

And this is hardly a comprehensive list of everything Dr. Google indicates. Basically, if you’ve got it, there’s a kombucha website that’ll tell you it can cure it. But can it?

Research and Evidence

A review of the literature indicates there has been a surprisingly large amount of scientific research performed on Kombucha and its bacterial-yeast cultures (SCOBY). There is evidence of antioxidant and anti-cancer cell effects in cells grown in the lab, as well as antibacterial and anti-fungal activity against a wide range of species.[5] In animal studies, kombucha has been shown to have antioxidant activity, control blood sugar levels, prevent DNA damage, and reduce damage to the liver (hepatoprotective) from select toxins.[6]

It should be noted that the above benefits are only partially protective effects (prophylaxis) however, and not mythical cures or body detoxes, and that some of the biological effects are attributed to common chemicals found in many teas and other drinks (e.g. ethanol, acetic acid, or polyphenols) rather than being something uniquely special to Kombucha itself.


Source: nanotechmag

Unfortunately, there isn’t any evidence that those benefits detailed above translate into human health and often when you try to apply these petri dish studies to the human body nothing happens.  In the case of the more extreme assertions such as curing cancer or AIDS, not only does no evidence exists but suggesting that proof does exist can be very dangerous if it encourages people to trust in a fizzy drink over evidence-based medicine to manage serious illness.[1]

When it comes down to the big question: “is it good for my health?”, there is very little or only poor-quality/anecdotal evidence to suggest specific human health benefits beyond, say, a humble cup of green tea. Currently, published review articles of the scientific literature conclude that human health benefits are unsupported, but lots of research is ongoing.[6]


Depends: low to moderate.

Broadly speaking it comes down to home-made (moderate) vs. commercial preparations (low). Retail brands should pose low risk due to quality controls over alcohol levels, acidity, and which bacteria/yeasts are present. There have been a few alleged cases of Kombucha-associated toxicity (e.g. nausea, headaches, pain, jaundice) although it’s only thought to pose a significant risk to people who are immunocompromised (e.g. HIV/AIDS patients) or those who suffer from certain gastrointestinal conditions.[6] There are mixed reports as to whether the beverage could actually be helpful or harmful for some conditions like Crohn’s Disease or irritable bowel,[7] but there’s no scientific research either way to support these claims. As with many probiotic-contain foods, pregnant women are suggested to avoid it.


Source: Experience Life.

The real dangers lies in home-made preparations where contamination with dangerous levels of pathogenic bacterial species may cause infection or poisoning.[8] Control of the chemical contents, particularly lactic and acetic acids may also cause health issues, with reports of lactic acidosis and nausea.[9]

The most concerning risk, as with any ‘superfood’, is the use of the product in place of evidence-based treatments for serious and potentially fatal medical conditions like cancer, AIDS, or diabetes.

The Chemistry

Kombucha starts life basically as sugary tea, containing various B vitamins, sugars (e.g. sucrose, glucose, and fructose), and anti-oxidants like polyphenols which are credited with many of the observed positive biological effects seen in the research.[8]  Any caffeine content depends on the types of tea used while other chemicals may or may not be present when the beverage is made from different starting materials like fruit juice. After fermentation, the mature Kombucha will also contain variable amounts of ethanol (drinking alcohol) and various organic acids (principally acetic acid) which are usually blamed for the negative biological effects reported.[8]

The Biology

Kombucha is prepared by a double fermentation process where the sugars in the tea are converted by yeasts to alcohol (ethanol) which is then converted to acetic acid by various bacterial species (Figure 3). The process produces carbon dioxide (CO2) as a biproduct giving the drink a fizzy quality.[1]


Figure 3: Fermentation of fructose sugar to ethanol and acetic acid. (see here for reading condensed chemical structures like fructose). This is one of the main processes but many different fermentation are going on in tandem.

The fermentation microorganisms are added in the form of a squishy mould-like pancake called SCOBY (symbiotic culture of bacteria and yeast – often called the “mother” or “Kombucha Mushroom”, Figure 4). There have been a huge number of different species isolated from different kombucha SCOBY’s depending on the source and so the exact microorganisms present are often unknown and very diverse. Most commonly, multiple species of acetic acid bacteria (acetobacter sp.) and variety of yeasts (e.g. Saccharomyces sp. and Candida sp.) are present.[6]

This exciting microbial pick-n’-mix is unfortunately why some SCOBY are contaminated with dangerous/pathogenic bacteria and yeasts, especially in home-made preparations of kombucha, which can lead to potential poisonings and infection. You can buy SCOBY for home use but some people grown their own using an existing retail kombucha drink as a starting source of the desired bacteria and yeasts, much like one would to make yogurt (Figure 5).[10] Unfortunately, there are all sorts of nasty microbes hanging out in our houses and on non-sterile equipment so homemade fermentations have a higher risk of getting unintended microbes contaminating your drink.

Figure 4: SCOBY ‘pancake’. Source: The Kitchn           Figure 5: White growth of new SCOBY. Source: Becoming Peculiar

As mentioned above, one of the fermentation products is ethanol which is largely converted to acetic acid. But due to the exciting diversity of the bacterial cultures and preparation methods, kombucha can be made alcoholic or not.[11] The rules[12] differ in different parts of the word, but here in NZ, a drink doesn’t count as booze unless it has over 1.15% v/v ethanol[13] so you can find bottles in lots of nice cafes and supermarkets and no one’s gonna raise an eyebrow if you grab one with brunch. Amusingly though, the presence of live yeasts can mean fermentation may continue over time, increasing the alcohol concentration in bottles, resulting in some drinks becoming quite boozy and some products having to be removed from shop shelves.[14] Could be a fun if surprising addition to your next healthy work lunch.

drunk minion

Source: Drunk Minion Twitter.

Final Thoughts

If you like the tangy flavour, see if the commercial brands fill a hole that regular old ice tea won’t, but personally I’d steer clear of home-made attempts unless you really know it’s not going to poison you. Drunk in moderation, and in absence of any personal tummy problems, it’s unlikely to do you any harm, but then it’s unlikely to do you any extra good either over a nice cuppa tea. Health-wise, it’s just another fizzy sugary drink in disguise for most people but it could have hidden risks for a few people and depending on where you’re getting it from. On that note, I’m off for a beer and a breather – shorter blog post next time me thinks.


References and Footnotes

[1] Kombucha 101: Demystifying The Past, Present And Future Of The Fermented Tea Drink. https://www.forbes.com/sites/christinatroitino/2017/02/01/kombucha-101-demystifying-the-past-present-and-future-of-the-fermented-tea-drink/#526191b54ae2. (accessed September 15, 2017).
[2] Wellness Mama: The Many Health Benefits of Kombucha. https://wellnessmama.com/23994/kombucha-benefits/. (accessed September 17, 2017).
[3] Food Renegade: Kombucha Health Benefits. http://www.foodrenegade.com/kombucha-health-benefits/. (accessed September 17, 2017).
[4] Wikipedia: Kombucha. https://en.wikipedia.org/wiki/Kombucha. (accessed September 18, 2017)
[5] Jayabalan, R.; Malbasa, R.; Loncar, E. S.; Vitas, J. S.; Sathishkumar, M. A Review on Kombucha Tea-Microbiology, Composition, Fermentation, Beneficial Effects, Toxicity, and Tea Fungus. Comprehensive Reviews in Food Science and Food Safety. 2014, 13, 538-550.
[6] Ernst E. Kombucha: a systematic review of the clinical evidence. Forschende Komplementarmedizin und Klassische Naturheilkunde. 2003; 10, 85-87.
[7] IBDrelief: Probiotic foods and IBD. https://www.ibdrelief.com/learn/probiotics-and-ibd/probiotic-foods-ulcerative-colitis-and-crohns-disease. (accessed September 19, 2017).
[8] BC Centre for Disease Control. Assessment of Kombucha tea recipe and food safety plan. Date requested: January 27, 2015.
[9] WebMD: The Truth About Kombucha. http://www.webmd.com/diet/the-truth-about-kombucha. (accessed September 19, 2017).
[10] Becoming Peculiar: How to start Brewing Kombucha without a SCOBY. http://becomingpeculiar.com/how-to-start-brewing-kombucha-without-a-scoby/. (accessed September 18, 2017).
[11] Kombucha Home: How to increase alcohol content of Kombucha Tea. http://kombuchahome.com/how-to-increase-alcohol-content-of-kombucha-tea/ (accessed September 19, 2017).
[12] Sale and Supply of Alcohol Act 2012. Public Act 120, 2012; Section 5, 1, b (ii).
[13] 1.15% ethanol percent volume per volume (% v/v), measured at 20 °C.
[14] BevNET.com: ‘Kombucha Crisis’ Fuels Progress. https://www.bevnet.com/news/2013/kombucha-crisis-fuels-progress/. (accessed September 15, 2017).

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