Article Summary: Kombucha Tea is a centuries-old source of probiotics, prebiotics, antioxidants, and detoxifying nutrients. On one hand, many recent peer-reviewed research articles have reported significant beneficial effects of Kombucha Tea consumption on gut health and the gut microbiome, but on the other hand, research also shows that issues with ingredient selection, production, storage, and transport can (but not always) diminish Kombucha’s beneficial effects on health. Understanding where to be optimistic and where to be cautious is key to understanding Kombucha Tea’s complex effects on health.
Table of Contents:
- A Snapshot of Kombucha Tea History
- What is Kombucha Tea? How is Kombucha Tea Made?
- The Three Ingredients of Kombucha Tea
- What Happens During Kombucha Fermentation? What NEW Health-Promoting Compounds are Formed?
- Does Kombucha Tea REALLY Improve Gut Health and Balance the Gut Microbiome? Let’s Review the Research
- Where CAUTION is Needed Interpreting the Research on Kombucha Tea Health Benefits
- A SOLUTION for Some of Kombucha Tea’s Potential Short-Komings
- Works Cited
This article takes a stance of cautious optimism regarding Kombucha tea.
There is a legitimate body of evidence in support of Kombucha’s beneficial health effects, and an equally legitimate set of reasons to interpret some Kombucha Tea research with caution.
This article unpacks this dichotomy, and through it, we explore Kombucha’s history, ingredients, fermentation process, health benefits, and more.
Let’s begin with Kombucha’s origin story.
A Snapshot of Kombucha Tea History
Records show that (A) kombucha consumption began in the Qin Dynasty (220 BC.) in northeastern China, when Kombucha became popular due to its energizing and detoxifying properties.
(B) Around the year 414 AD, a Korean doctor named Kombu became famous when he used fermented tea to treat the intestinal problems of the Chinese emperor. He later introduced the beverage to Japan, where it became popular, and won the name Kombu-cha, or tea of Kombu [2, 3].
(C) Given its nutritional and functional benefits, Kombucha spread throughout the world, particularly in Europe. Studies show that it first arrived in Russia via commercial sea routes and (D) expanded to Germany and Italy in the 20th century, shortly after World War II.
In the 1950s, (E) Kombucha also became popular in France and North Africa [4]. Recently, Kombucha has experienced a renaissance, capturing huge market share for its distinct taste and numerous purported health benefits [5].
What is Kombucha Tea? How is Kombucha Tea Made?
Simply put, Kombucha is fermented sweet tea. It is made from three ingredients: tea, sugar, and microbes.
To make Kombucha, we follow these steps: Infuse tea. Add sugar. Inoculate with a “Symbiotic Culture of Bacteria and Yeast,” or SCOBY. Wait patiently.
While seemingly simple, tea, sugar, and microbes are not in fact unitary things, but rather broad classes of things that include a lot of variability.
Let’s look at the different shapes and forms of these three Kombucha ingredients, and how those variations might affect our final Kombucha brew.
The Three Ingredients of Kombucha Tea
Kombucha Ingredient #1: Tea
Authentic Kombucha (i.e. that brewed and served by Kombu himself) is made from Camellia sinensis-based Tea, not Herbal Tea. If you need a refresher on that distinction, see Chapter 1 of our Masterclass on Tea.
Using real tea (i.e. C. sinensis-based tea) in Kombucha production is a critical detail because many phytonutrients unique to tea leaves are both what feed the beneficial microbes during fermentation, and what provide antioxidant properties of Kombucha Tea itself. This is why Kombucha Tea has been described by researchers as a double power [6].
For example, catechins – the main antioxidants in tea leaves – were abundant in Kombucha made from Green and Black teas, but not detectable in Kombucha made from Rooibos (an herbal tea) [7].
In turn, Green and Black Tea Kombuchas were much stronger antioxidant beverages than Rooibos Kombucha.
So, narrowing ‘tea’ down to C. sinensis is helpful, but tea aficionados know that this still leaves a world of possibilities on the table.
Which of the six major tea types is best for Kombucha? Does Oolong Tea Kombucha have more health benefits than White Tea or Green Tea Kombuchas?
You see, each tea type Koms to the table with its own strengths and short-Komings.
Let’s examine the most famous rivalry between tea types, Green vs Black.
The above study concluded that Black Tea Kombucha (BTK) was a better antioxidant beverage than Green Tea Kombucha (GTK) due to a more diverse and abundant profile of antioxidant molecules. However, GTK fought pathogenic bacteria and suppressed human tumor cell growth more effectively than BTK [8].
A more recent study similarly showed that GTK was a more effective antibacterial agent than BTK [9]. Replicated findings make me feel warm and fuzzy inside.
So, just like the findings in normal non-Kombucha Green and Black Teas, there are clear differences, but no clear “best.” The rivalry lives on.
Beyond Green and Black, Oolong Tea Kombucha (OTK) stimulated antioxidant and detoxification pathways [10], while White Tea Kombucha (WTK) and Pu-erh (Puer) Tea Kombuchas (PTK) were also potent antioxidant drinks [11].
For now, we can say that tea makes the best Kombucha Tea, however which tea… is Komplicated.
Kombucha Ingredient #2: Sugar
Just like Ice Cold Coors Light, Cold as the Rocky Mountains (official beer sponsor of Wu Mountain Tea), a sugar- or starch-based fuel is needed for microbial fermentation.
As with Whiskey, the starch used during fermentation greatly affects the taste, quality, and, importantly for Kombucha, the bioactive properties, of the final beverage.
A recent study used two sugar types, cane sugar or coconut sugar, to produce Black Tea Kombucha, Green Tea Kombucha, and White Tea Kombucha [9].
They found that sugar type could (but not always) affect the pathogen-fighting properties of Kombucha Tea.
For example, in suppressing the pathogen S. typhi, GTK made from cane sugar was over 100% more potent than the same Green Tea fermented with coconut sugar (red rectangle). However, in assessing effects of GTK against E. coli, sugar type sugar made no difference (blue rectangle).
In suppressing fungal pathogen C. tropicalis, sugar type made a significant difference for every Kombucha Tea type (green rectangle). Conversely, in suppressing L. monocytogens, sugar type made no difference for Black Tea and White Tea Kombuchas, and only a borderline significant difference for Green Tea Kombucha (purple rectangle).
Beyond the antimicrobial properties, the probiotic properties (the beneficial living microbes in Kombucha Tea that we ingest) are also fluctuating with sugar type.
Some probiotic communities were only detected in Kombucha Tea made from coconut sugar, regardless of tea type (red rectangle). Conversely, other probiotics survived only in cane sugar-, but not in coconut sugar-made Kombucha, regardless of tea type (blue rectangle) [9].
The probiotic communities in Kombucha not only colonize our guts and provide beneficial effects there, but they also generate new bioactive nutrients during fermentation. Therefore, changes in probiotic communities within the Kombucha can amount to significant differences in Kombucha’s composition and ultimate effects on health.
So, we can see that sugar type absolutely effects some bioactive properties of Kombucha, but not others.
Bitter-sweet, no?
Kombucha Ingredient #3: Microbes
Now let’s address the elephant in the room… Kombucha Tea is made using a objectively disgusting-looking slime mat…
Look, folks … childbirth is not pretty per se, but we call it is the miracle of life, don’t we? Try your best and get over the slime mat – Kombucha is miraculous too.
Our SCOBY has two key beneficial actors, bacteria and fungi.
Kombucha Tea Fungi / Yeast: The Booze Brewers
Kombucha yeasts are key in creating the distinct composition and sensory qualities of Kombucha [12]. To date, a wide range of different yeast species have been discovered and isolated from Kombucha culture [13-15].
Chief among Kombucha fungi are saccharomyces-type yeasts that specialize in converting sugar into booze (ethanol). A few typical Kombucha yeasts are pictured and characterized below [16].
Common qualities of Kombucha yeasts include sugar fermentation and stress tolerance, making them ideal candidates for the painstaking task of turning sweet tea into Kombucha Tea.
Kombucha Tea Bacteria: The Acid Makers
Acetic acid bacteria (AAB) represent 80+% of Kombucha bacteria [15, 17].
AAB work down the assembly line from Kombucha yeast, turning the ethanol they produce (not-so-healthy) into acetic acid, a health-promoting organic acid [4, 18].
AAB from Kombucha are also able to form symbiotic relationships with beneficial strains in the gut [18, 19].
Besides AAB, Kombucha bacteria also include Lactic Acid Bacteria (LAB).
LAB are gut health-promoting, anti-inflammatory, anti-oxidative, and interestingly, beneficial for mood-enhancement, offering calming and anti-anxiety effects through the gut-brain axis
[20-28].
Kombucha LAB produce antibacterial molecules, called bacteriocins, that work alongside acetic acid to antagonize pathogens [6]. Even today, new bacteriocins formed by LAB during Kombucha fermentation are being isolated and characterized for the first time [29].
Those were our 3 primary raw ingredients of Kombucha Tea (Tea, Sugar, and Microbes).
Let’s now explore Kombucha fermentation to understand how these three raw ingredients transform into Kombucha Tea.
What Happens During Kombucha Fermentation? What NEW Health-Promoting Compounds are Formed?
During Kombucha fermentation, our SCOBY consumes the sugar and some of the tea, digests them, and forms new health-promoting nutrients.
What are some of these new ingredients formed during Kombucha fermentation?
New Kombucha Ingredient Formed During Fermentation #1: Bacterial Cellulose
Brace yourself. During Kombucha fermentation, acetic acid bacteria (AAB) take individual glucose molecules and glom them together at a speed of 200,000 GLUCOSES PER SECOND PER BACTERIAL CELL to form bacterial cellulose (BC). BC is a form of cellulose SO PURE that it makes plant-based cellulose look like Ohio River water [16, 30].
Scientistsare fascinated by BC formed during Kombucha fermentation. The figure below shows that in the eyes of research scientists, BC production is as interesting as the entire topic of Kombucha Tea health effects.
Kombucha BC was first hypothesized in 2008 to be a key nutrient that mediates at least some of the observed benefits of Kombucha Tea [33]. Recent studies have since confirmed impressive wound-healing and antimicrobial properties of BC, properties that less pure plant-based cellulose lacks [31, 34-36].
New Kombucha Ingredient Formed During Fermentation #2: Organic Acids
If you’ve had Kombucha before, you’ll have noticed that twang… that tangy twangy *author smacks lips while writing* tangy twang that it’s got.
That is from organic acids produced by AAB and LAB during fermentation.
Organic acids not only create the distinctive twang of Kombucha Tea, but also mediate several of Kombucha’s health benefits.
Acetic Acid
Regardless of major tea type, acetic acid levels rose 450-fold between day 0 and day 14 of Kombucha fermentation (red rectangle) [11].
Acetic acid fights human pathogens such as Salmonella, Staphylococcus aureus, E. coli, and H. pylori [37-40].
Glucuronic Acid
Glucuronic acid (GlcUA) drives the detoxifying properties of Kombucha Tea [41].
Through a process called glucuronidation, GlcUA attaches to toxins in the liver, then kindly escorts them out of the body [42]. Even Wikipedia mentions Kombucha when talking about GlcUA.
New Kombucha Ingredient Formed During Fermentation #3: Phenolic Compounds
Phenolics are a broad and important class of plant antioxidants found in tea leaves (including the catechins mentioned earlier).
In Chapter 2 of our Masterclass on Tea, this was the first group of tea molecules that we discussed.
Phenolics are responsible for the health benefits of normal (unfermented) tea, and in turn, mediate many health-promoting properties of Kombucha Tea.
During fermentation, tea polyphenols that are larger in size, like EGCG in Green Tea, or Theaflavin in Black Tea, are partially degraded by SCOBY and form many different smaller phenolic compounds.
A fresh tea leaf may only contain a few dozen unique types of phenolics, however over 100 different phenolic compounds were reported from a 10-day Kombucha tea brew [8].
As a result of this splintering and fragmenting of large tea polyphenols into many unique smaller phenolics, the overall phenolic profile shifts dramatically.
How does this transformation affect total antioxidant power of the brew?
Data are inconclusive on this point; some studies found antioxidant power to increase with Kombucha fermentation [7, 44, 45], while one recent study found a decrease in total antioxidant power following fermentation [11].
New Kombucha Ingredient Formed During Fermentation #4: Vitamins and Minerals
Forget your One-A-Day Multi – Kombucha Tea SCOBY are forming vitamins and minerals during fermentation (still take the multi though – I was just sayin’).
Comparing day 0 to day 14, levels of available Magnesium, Potassium, and Calcium all increased significantly with Kombucha fermentation, regardless of Tea type (White vs Green vs Black) or sugar type (coconut vs cane) [9].
In addition to essential minerals, Kombucha SCOBY are efficient producers of vitamins; Vitamin C and various different B vitamins all increased significantly with Kombucha fermentation [46, 47].
Does Kombucha Tea REALLY Improve Gut Health and Balance the Gut Microbiome? Let’s Review the Research
Let there be no doubt here. Consuming vitamins and minerals and phenolic compounds is good for health [48]. In other words, if Kombucha really does contain all the things we just said it does, many bodily systems would see benefit.
So, rather than explain the 78 different organs that benefit from adequate Vitamin C or Potassium nutrition, let’s explore one more complex health benefit of Kombucha that is both fascinating and on the cutting edge of Kombucha Tea research; the gut health effects [49, 50].
‘Gut Health’ is a tricky term because it includes many different aspects.
Let’s focus just on the microbiome of the gut, or the trillions of bacterial and fungal cells that inhabit each and every one of us.
In order for something to ‘support a healthy gut microbiome’ it should:
- suppress harmful communities.
- support beneficial communities
Let’s see how Kombucha Tea fares in these two tasks.
How Kombucha Tea Improves Gut Health #1: Suppressing Harmful Communities of the Gut
Kombucha Tea has been shown to suppress many types of pathogenic bacteria and fungi that commonly create disease and illness in humans [13, 51, 52].
As mentioned before, the following components of Kombucha Tea have proven antimicrobial properties:
- Phenolics from tea leaves.
- Bacteriocins from LAB.
- Acetic Acid from AAB.
- Vitamins and minerals that act as critical co-factors, or ‘helper molecules’ for our immune cells, providing indirect antimicrobial activity.
- Probiotic microbes that compete with pathogenic communities in the gut for resources.
As these increase during Kombucha fermentation, the antimicrobial capacity of Kombucha Tea increases as well.
Between fermentation days 0 and 14, the capacity of Kombucha Tea to combat the pathogens E. coli and Salmonella increased significantly [13].
How Kombucha Tea Improves Gut Health #2: Supporting Beneficial Communities of the Gut
Kombucha is both a source of beneficial communities themselves (a probiotic), and food for beneficial communities to survive and thrive (a prebiotic).
Probiotics are defined as “live microorganisms which when administered in adequate amounts confer a health benefit on the host” [53].
Many of the Kombucha microbes we’ve mentioned thus far fit this definition, including Lactobacillus and Acetobacteria.
A key question in evaluating probiotics is whether they can survive the harsh stomach environment, with low oxygen pressure, bile salts, and pH of 2.
As some researchers recently described [18], microbes that can survive the low oxygen and low pH conditions of Kombucha fermentation are almost by definition able to survive and proliferate in the gut. Kombucha fermentation is like BUDS for the microbial Navy SEALS of the gut.
One recent study actually tracked the series of events that followed successful colonization of mouse guts by Kombucha probiotics:
- Beneficial gut communities increased.
- Mouse intestinal cells produced more ‘tight junctions’ (the proteins that hold together the intestinal lining).
- Intestinal barrier integrity improved.
- Leakage of inflammatory molecules from the gut into circulation decreased.
- Systemic inflammation decreased.
- Glucose tolerance improved.
- Liver damage was ameliorated.
This study demonstrated how numerous downstream benefits on health occurred follwonig the successful colonization of the gut by Kombucha probiotics (depicted by Xu et al. below) [54].
A separate study from 2019 simlarly found that Kombucha allowed Lactobacillus (a major type of LAB) populations to increase, and NAFLD (non-alcoholic fatty liver disease) to decrease, perhaps through the same series of events described two years later by Xu et al. [55].
On the prebiotic side, residual (undigested by SCOBY during fermentation) tea leaf phytonutrients in the final Kombucha Tea act as fuel in the gut for beneficial communities [56]. They feed on the leftovers that Kombucha SCOBY didn’t get to during fermentation.
A human trial found that Green Tea (the normal unfermented tea) functioned as a prebiotic that fueled Bifidobacteria, a beneficial community with similar mood-enhancing effects as Lactobacillus [57], showing that tea leaf nutrients can feed beneficial bugs of the human gut.
It remains unclear which bioactivenutrients from tea support beneficial communities most – some say polyphenols [56, 58], while others recently said tea alkaloids [59]. Regardless, consistent and measurable prebiotic effects of tea consumption have been observed [56, 58-63].
So… can Kombucha “improve gut health”? Yes, it can. For these reasons;
- Pathogens are suppressed directly by antimicrobial molecules
- Pathogens are suppressed indirectly through competition from beneficial communities
- Beneficial populations increase from direct consumption (probiotic effects)
- Beneficial populations increase from tea phytonutrient intake (prebiotic effects)
Now, based on this evidence, we have legitimate reason to be optimistic about the gut health-promoting effects of Kombucha Tea (and probably other beneficial effects too).
So, where is caution necessary when reading and interpreting research on Kombucha Tea health benefits?
Where CAUTION is Needed Interpreting the Research on Kombucha Tea Health Benefits
Kombucha Fermentation CONDITIONS Vary A LOT Across Experiments
One reason you must be cautious when interpreting Kombucha Tea research is that there are so many variables that change from one Kombucha brew to the next.
While only the simple product of 3 ingredients and 1 process (fermentation), variability across ingredients and the fermentation process is enormous.
For starters, the quality and quantity of bioactive compounds in Kombucha were measurably affected by SCOBY source [64], sugar and tea concentration [65, 66], fermentation time [67] and fermentation temperature [68, 69].
Moreover, across experiments, Kombucha fermentation parameters are not at all standardized.
A review article from 2022 compiled all the different fermentation conditions used in all the known Kombucha experiments conducted to date [45]. In this review, you can see 5X variations in key parameters like tea concentration, sugar concentration, and fermentation time/temperature.
As you can imagine, these variable Kombucha fermentation conditions directly affect key bioactive ingredients in Kombucha Tea, such as bacterial cellulose [71].
Low-Grade and Antioxidant-Poor TEA LEAVES Produce Low-Grade and Antioxidant-Poor KOMBUCHA
As we discussed in Chapters 4 and 5 of the Masterclass, low-grade tea leaves contain less bioactive nutrients than high-grade tea leaves. In turn, research shows that Kombucha Tea bioactivity is proportional to that of the original tea leaves used to brew it.
Below, I applied the data from one study to conduct my own regression analysis. The data show that total polyphenol content of the final Kombucha tea was significantly correlated with total polyphenol content of the original (unfermented) tea [11].
Now combine this with the fact that total tea polyphenol content across a sample set of 30 teas (including all 6 tea types) ranged 10-fold [70]. This suggests that the antioxidant activity of Kombucha is capable of 10X fluctuations even when using true Camellia sinensis tea.
Storage and Transport KILL OFF Beneficial Probiotics in Kombucha Tea
Just because your Kombucha was probiotic-rich when it left the brewery doesn’t mean it is still
probiotic-rich when you bought it at the supermarket.
One study showed that the survival rate of lactic acid bacteria (LAB) in Kombucha Tea was only 0.98% by the 8th day of storage [66].
If you can’t keep the beneficial microbes alive, you lose the probiotic effects of Kombucha, which is HALF of Kombucha Tea’s so-called “Double-Power” [6].
Extreme Scarcity of Data from HUMAN TRIALS on Kombucha Tea Health Effects
Lastly, experiments measuring the actual effects of Kombucha Tea consumption in humans are scarce.
One article from 2018 attempted to write a systematic review of the human data on Kombucha, only to discover that there was 1 human trial published at the time [72].
A lack of human data does no disprove anything, but it is certainly something to keep in mind when evaluating the evidence surrounding Kombucha Tea’s purported health benefits.
A SOLUTION for Some of Kombucha Tea’s Potential Short-Komings
Looking at some of these issues surrounding Kombucha, I surmised that a great way around the problems of Kombucha transport, storage, and low-grade ingredients might be to BREW YOUR OWN ‘BOOCH.
With home-brewed Kombucha, you select your own high-quality ingredients and don’t require any storage and transportation. This way, Kombucha quality, purity, and bioactivity is guaranteed.
If you’re unsure where to begin, there’s many Kombucha home-brew guides and resources available to help kickstart your journey. Here are a few:
In conclusion, I remain cautiously optimistic about the health benefits of Kombucha Tea.
I hope this article helped you better understand the complex and ever-changing picture of Kombucha Tea science.
If you’re more of an audiovisual learner, I attached the YouTube video version of this very blog article below. It follows along with the same citations as those listed in the works cited of this article below.
Thanks for reading!
Dylan
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