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Kombucha’s “health halo” isn’t totally made up, but it’s ahead of the human evidence. Fermentation can increase antioxidant availability and generates a complex mix of organic acids (like acetic and glucuronic) that may help explain kombucha’s antimicrobial and digestion-supportive reputation. Still, most studies are not in humans, and outcomes depend heavily on how it’s made, fermentation time, residual sugar, alcohol content, and contamination control all change the final product. If you drink it, treat kombucha like a functional food: choose reputable brands (or brew carefully in glass), start small, and don’t confuse “potential” with “proven.”
Make no mistake about it, people are brewing kombucha all over the world. Walking past the entire "booch" section in Whole Foods, you could be forgiven for writing it off as a North American fad. In truth there is nothing local or recent about kombucha brewing.
Using a "tea fungus" or SCOBY to ferment sweetened teas dates back to 220 BC in ancient Manchuria in the North of present-day China before spreading through Japan, Russia, and then the West.
Regional popularity has waxed and waned in the past 100 years. Still, there is no doubt that kombucha has enjoyed a tremendous renaissance of late, fully back in style with the study of the microbiome and the rising trendiness of all things probiotics.
There is a myth that no real science exists to support kombucha's purported health benefits, and that all claims are merely dubious anecdotes or placebo. But that is simply not true. There is, in fact, a bonafide mountain of scientific evidence of kombucha's benefits… Unfortunately it has generally been done on rats, pigs, dogs, chickens, ducks, cows, rabbits, and in test tubes.
Traditional kombucha is made with three ingredients: tea, sugar, and SCOBY. To make your own, you don't need to know what a SCOBY is beyond the fact that it is the slimy, off-white lilypad that likes to collect at the surface of kombucha brews and is the agent responsible for their fermentation. When one brew is done, take that firm-but-squishy pad out and add it to another glass jar of sweetened black or green tea, and in seven days or so it too will be fermented into kombucha. At any point, refrigeration will stop fermentation from continuing and render the drink safe to store cold for up to six months.
After the bacteria and yeast feed happily on the sucrose and the nitrogen in tea leaves, the drink transforms completely. What starts as a simple sugary tea becomes a deluxe chemical cocktail of organic acids, B, E, and A vitamins, enhanced tea polyphenols, a wide array of minerals, enzymes, probiotic bacteria, aminos, fibre, and more. It even contains vitamin C, which the SCOBY is, amazingly, able to create from sugar! There is a fairly strong argument to be made that even in the absence of randomized, double-blind human trials, the ingredients of finished kombucha alone are enough to justify its place in a healthy lifestyle. Vitamin C, for example, has tons of human evidence.
In the plentiful scientific literature that does exist, kombucha has demonstrated an impressive range of health benefits that hold tremendous promise for its potential in humans. To date, studies in animals and in test tubes have shown that kombucha offers liver and detoxification support, anti-tumour qualities, cancer inhibition, antimicrobial effects against pathogens, immune revival, as well as benefits for diabetes, cardiovascular and neurodegenerative diseases. Many of these benefits are related to the drink's antioxidant power, which, thanks to fermentation, is much more effective at free radical quenching than the sum of its parts (such as the starting tea).
Detractors are generally quick to point out that people have hurt themselves drinking kombucha. And it is undeniable improper use has resulted in even some serious health conditions. Drinking too much, over-fermentation or contaminated brews seem to be the most common causes of documented liver damage and acidosis.
The acidity of kombucha also means that it must always be brewed in glass as it will easily leach lead from ceramic containers. While the FDA has concluded that commercial kombucha is generally quite safe, homebrews are totally unregulated and subject to all manner of folly. There are some liver, heart, and kidney conditions, as well as pregnancy, where drinking kombucha is categorically contraindicated.
The takeaway regarding safety is that sticking to reputable manufacturers as a consumer is warranted. And if you are making it at home, be as meticulous as possible with good practices like sterile equipment and established brewing parameters.
Supermarket kombuchas are often oversized and fermented in fairly short windows for a sweet and easy drinking soda alternative, but the sugar content alone has led many to wonder if such a beverage could really be considered healthy at all.
Ayed, L., Abid, S. B., & Hamdi, M. (2016, November 26). Development of a beverage from red grape juice fermented with the Kombucha Consortium - Annals of Microbiology. SpringerLink. https://link.springer.com/article/10.1007/s13213-016-1242-2
Banerjee, D., Hassarajani, S. A., Maity, B., Narayan, G., Bandyopadhyay, S. K., & Chattopadhyay, S. (2010). Comparative healing property of Kombucha Tea and black tea against indomethacin-induced gastric ulceration in mice: Possible mechanism of action. Food & Function, 1(3), 284. https://doi.org/10.1039/c0fo00025f
Cetojevic-Simin, D. D., Bogdanovic, G. M., Cvetkovic, D. D., & Velicanski, A. S. (2008). Antiproliferative and antimicrobial activity of traditional Kombucha and Satureja montana L. Kombucha. https://jbuon.com/archive/13-3-395.pdf
Considering the demonstrated benefits for animals, the constituent ingredients which have been studied extensively on their own, and the massive level of commercial kombucha consumption worldwide, swathes of kombucha researchers have reiterated in chorus the pressing need for human trials. Many have even gone so far as to outline in detail how those trials ought to be conducted. In other words- the time has come for kombucha studies on humans, and we are likely to see many of them in our lifetime.
The word SCOBY is actually an acronym: Symbiotic Culture Of Bacteria and Yeast. In a sense, this phrase goes a long way in explaining how kombucha is different from ferments like sauerkraut or most alcoholic drinks. Kombucha tea is not made from small handfuls of yeast strains like beer; it is the dozens of different yeast and bacterial strains in the SCOBY working synergistically that make the drink its own very unique and particular specimen.
While proportion and population vary from brew to brew, several mainstays of every SCOBY include the acetobacter bacteria that create acetic acid, giving kombucha its tang, and the yeasts that produce carbonation (fizz) and small amounts of ethanol. One important bacteria character called k.xylinus is responsible for building the cellulose mat of the SCOBY, providing its structure and rubbery texture, and yeasts temporarily aggregate to form a scaffold, allowing it to do this job.
In such ways, the many bacteria and yeasts that make up the SCOBY cooperate, but they also compete, and the result is a fairly stable system of checks and balances that keep any one element from predominating- or admitting many outsiders. And since the fermentation process drops the pH of the tea and makes the whole scene more acidic, the entire jar quickly becomes a veritable fortress against contamination by nasty microbes, fungi or mould. This effect is added to by the SCOBY's oxygen-loving affinity for covering the tea's entire surface area at the top of the jar- it is really as though the constituents of the SCOBY are claiming the tea for their own.
Epigallocatechin gallate (EGCG), the most famous antioxidant from green tea associated with much of its health benefits, is present in kombucha made from green tea even more abundantly than in the original green tea. This is owed to the chemical liberation achieved by the fermentation process, massively increasing the overall antioxidant effect of the drink. And again, EGCG, just one of the tea polyphenols common in kombucha, has been extensively studied in humans.
Like all fermented vinegary things, kombucha is acidic due to the abundance of postbiotic organic acids like acetic, lactic, glucuronic and gluconic acids. Generally the longer the fermentation time is, the more abundant the acids and the lower the pH will be. Meanwhile, more and more of the sugar is consumed by the SCOBY, meaning that stopping fermentation sooner will leave more sugar undigested, hence a sweeter drink.
Typically at seven days of fermentation the kombucha will be slightly effervescent but still sweet, and by 14 it will taste more like vinegar. By 21 days, 80 per cent of the sugar is gone. This clean continuum, from sweet and easygoing in the early stages to funky and tangy later on, makes it easy and intuitive for home-brewers to craft for their own taste.
While it's often touted as a probiotic thanks to its friendly bacterial members and has indeed been shown to protect and tonify the gut membrane, kombucha is also an antibiotic, helping to kill and antagonize other less friendly bacteria and yeasts. This quality was initially ascribed to acetic acid, a known antimicrobial. Still, in studies, kombucha has been shown to be far more effective. In other words, vinegar may play a role, but it is not the whole story.
Another prominent organic acid in the milieu is glucuronic acid, which has profound implications for detoxification because it can latch onto toxic metals and chemicals in mammals and pull them out of the body. In doing so, glucuronic acid prevents nasty xenobiotics from accumulating, taking a load off of the kidneys and the liver. Humans can also convert glucuronic acid into glucosamine and chondroitin-sulphate, therapeutic compounds used regularly to treat osteoarthritis symptoms because they support cartilage, collagen, and joint fluid.
Other organic acids like gluconic and ascorbic acid (aka vitamin C) massively aid iron absorption, promoting energy and preventing anemia, as do kombucha's generous servings of B6 and B12. These components make kombucha an appealing prospect for vegans and vegetarians.
More anecdotally, users have reported improved digestion, regulated elimination, reductions in acid reflux, getting sick less often, clearer skin and improved joint mobility.
Alternatively, medical grade kombuchas sold in health food stores that do not require refrigeration may actually be the best place to start for the curious would-be booch enthusiast. These have been fermented for months in carefully controlled environments to create large quantities of organic acids with a minuscule amount of remaining sugar.
And no matter what kombucha you drink, taking it slow and keeping quantities small seems to be both the safest and most beneficial approach. Some people new to the drink can even find that 4 oz will upset their stomach.
But regardless of how much you can tolerate, drinking 1 to 2 tablespoons of properly brewed kombucha 20 minutes before a meal or so (much in the same vein as apple cider vinegar) is likely the best course of action. Not only will this be a safe and effective dose for most of us, but it should help with digestion when taken pre-meal in the same way vinegar would… while offering a smorgasbord of other goodies to boot!
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Tran, T., Grandvalet, C., Winckler, P., Verdier, F., Martin, A., Alexandre, H., & Tourdot-Maréchal, R. (2021). Shedding light on the formation and structure of Kombucha Biofilm using two-photon fluorescence microscopy. Frontiers in Microbiology, 12. https://doi.org/10.3389/fmicb.2021.725379
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Watawana, M. I., Jayawardena, N., Gunawardhana, C. B., & Waisundara, V. Y. (2015a). Enhancement of the antioxidant and starch hydrolase inhibitory activities of King Coconut Water (cocos nucifera var. aurantiaca) by fermentation with kombucha ‘tea fungus.’ International Journal of Food Science & Technology, 51(2), 490–498. https://doi.org/10.1111/ijfs.13006
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Lead image by Katherine Sousa.
