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What is Kombucha? A Dietitian's Guide To Fermented Tea

Researched and Written by:
Richelle Godwin, RDN Richelle Godwin, RDN

Kombucha is perhaps the most loved and hated drink in the health world right now. Some people are obsessed with it, and claim it is a probiotic-rich elixir here to save the world. While others say it is nothing but expensive soda and full of hot air! Well, in this article, we’re going to put kombucha under the microscope and discover what it is made from, what ingredients are actually inside it, as well as how it can potentially benefit and harm you.

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Table of Contents

    What is kombucha?

    So just before we get into the nitty gritty, let’s first look at what exactly kombucha is. After all, the name kombucha sounds mysterious - like some sort of magical tonic Gwyneth Paltrow would probably bathe herself in and sell for $90 a glass. 

    But here’s the thing: kombucha has been around for over 2000 years and is actually just sweetened tea that has been fermented.  That’s it!

    So you know exactly what this looks like, here is the 5 step process to make kombucha...

    1. First, you brew some black or green tea.
    2. Then you mix in some table sugar, remove the tea bag or leaves, and let it cool down.
    3. Once it's at room temperature, you add in a SCOBY, which I’ll explain in a minute, as well as some kombucha from a previous batch. 
    4. And now all you need to do is cover it with a breathable cloth and let it ferment away at room temperature for 1-2 weeks.
    5. Then you have kombucha!  

    In other words, kombucha is a brewed drink and made in a similar way to other fermented drinks like kefir or beer.

    What is a SCOBY?

    I mentioned the word SCOBY just before, and it is really the star of the show. I cover what it is in great detail in our separate article on SCOBYs, so let’s cut to that for a second...

    So there you go, pretty cool, right?! 

    And if you want to learn more about using a SCOBY and taking care of it, you can read that full article by clicking the link below.

    What does kombucha taste like?

    I’m sure you’ve probably tried kombucha before, so what I want to do here is just explain to you what properly brewed kombucha should taste like and explain why it tastes like that!

    Okay, so I have some original unflavored kombucha right here that I made myself.  And let me act like a Napa Valley wine snob for a minute.  

    It tastes a bit like tangy, sparkling cider. 

    There’s hints of sweetness in there, but big sour notes too, along with some lovely bubbles.  Meaning, there is a nice balance and exactly what a correctly brewed kombucha should taste like.

    Now if you want to geek out with me for a second, let’s quickly look at why 

    kombucha tastes like this.  So the Yeast in your SCOBY eats up a lot of the sugar in the sweetened tea, turning it into carbon dioxide, which gives us the bubbles, as well as alcohol.  Then the bacteria in the SCOBY eat up most of the alcohol  and turn it into acetic acid.  And that organic acid is what gives the sour taste. 

    Kombucha can also be flavored after it has been brewed.  We call this a second fermentation   For example, some people add in dried fruits - or their juices - and others even add in herbs & spices like ginger. 

    These flavors can work really well to soften the tangy taste.

    What healthy ingredients are inside kombucha?

    There is SO MUCH Misinformation out there on what is actually inside kombucha.  Some people say it is filled with probiotic superheroes, and that when you drink it, you are sending down an army of bacterial buddies to transform your gut health.  While others say it is just fizzy tea with a tang. 

    With so many conflicting stories, our research team at Essential Stacks and I decided to do some digging. 

    And like with all our articles you can find our studies and references in the description below.

    Here is what we found.  


    Most kombucha, whether made at home or bought in a store will contain some probiotics.  But How much and What types of probiotics you get, varies greatly.   

    So first up let’s talk about Homemade kombucha.

    Studies have found a variety of microorganisms in homemade kombucha, including bacterial strains from these families Komagataeibacter (formerly Gluconacetobacter), Lactobacillus, Acetobacter, as well as Yeast strains from these families, among others Saccharomyces, Zygosaccharomyces, Kluyveromyces.

    So a lot of people are quick to claim that Homemade kombucha is packed with probiotics!  Unfortunately, it is not that clear cut.

    For starters, not all of these strains of bacteria and yeast will meet the definition of a probiotic.  Meaning some may not confer a benefit to us humans.

    Secondly, the strains found in homemade kombucha can VARY greatly, depending on the SCOBY being used.

    And finally, the amount of CFUs of probiotics made through natural fermentation and thus found in homemade kombucha is unclear.  In fact, it is a huge point of contention. 

    Who knew the probiotic content of homemade kombucha could be so complicated?!  But if you’re game to deep dive into the research with us and see exactly what we found, then check out our Kombucha Benefits article.  

    Now, how does Store-bought kombucha compare?  

    Well in fact, we analyzed the top 10 brands for you and the results were interesting.  Some contained just a few hundred million CFUs of probiotics in a serving, while others had up to 8 billion CFUs.  Many didn’t state a specific amount, instead opting to hide behind vague language like “Billions of live cultures per bottle”.  

    Just as importantly, these probiotic amounts were calculated at time of bottling. 

    So how many CFUs you likely get when buying your kombucha weeks or months after it has been made, is completely unknown.

    In terms of the types of probiotics found in commercial kombuchas, once again we found a big variance across the brands.  Some were able to PINPOINT the strains found in their formula, while others went full Coca Cola on us and simply said it was a “proprietary secret”.

    None of this sat well with us, so we decided to do a full investigation into the top brands and if you want to see what we found, you can read our kombucha brands comparison article, or download our comparison tool.

    So what other goodies are hiding in this glass of kombucha? 

    Organic acids

    Kombucha is well known to be home to lots of organic acids such as these [card goes up with...

    Acetic acid, Gluconic acid, Glucuronic acid, Lactic acid, Citric acid, Tartaric acid, Usnic acid, Malonic acid, Malic acid, Pyruvic acid, Gallic acid.

    And our research suggests they might have Antimicrobial effects - meaning they can Kill or stop growth of BAD bacteria - as well as being potentially helpful for liver protection and detoxification.


    Unsurprisingly, since kombucha is made from black or green tea, it also contains polyphenols. 

    And these are exciting as they may act as Antioxidants to protect cells from damage & reduce the risk of disease - or possibly reduce inflammation, lower blood pressure and stabilise blood sugar levels.  

    What’s interesting, is that studies have observed that Polyphenol levels are higher in kombucha than in the original tea.  Meaning the fermentation process can promote polyphenol levels. 

    The research team and I loved this finding! 

    And so we did a little more digging for you to find out how to get the most polyphenols in your kombucha. And the answer is to make it at home, using green tea, and let it ferment for approximately 2 weeks, as researchers observed that the Highest concentration of polyphenols are on the 14th day of brewing. 

    Amino acids

    Thanks to the tea and fermentation process, kombucha also contains helpful amino acids.  My absolute favorite is L-Theanine , which can have a calming effect.  I’ll talk more about this in a minute when we look at the caffeine component of kombucha.

    Vitamins & minerals

    Finally, you can also find vitamins and minerals in kombucha, which you can see here:

    Vitamins: Vitamin B1, Vitamin B6, Vitamin B12, Vitamin C

    Minerals: Copper, Iron, Manganese, Nickel, Zinc 

    Some come from the tea itself, others from the fermentation process, and the rest from any fruit or fruit juices added in after the initial fermentation.  But before we get carried away thinking kombucha is some sort of liquid multivitamin, let's be clear here: these Micronutrients are found in very small amounts.

    What are the potentially troublesome ingredients in kombucha?

    With Alcohol, caffeine & sugar present in most kombuchas, you could be mistaken for thinking this is more of a health drink for Mel Gibson than us regular people. 

    And with lawsuits filed against several popular brands in recent years for Misleading claims about alcohol and sugar content, you might be worried kombucha is some sort of wolf in sheep's clothing. 

    But how bad is it really? 

    Well, here’s what our research team found…


    First, there is some alcohol in kombucha. Homemade kombucha typically has around 1% alcohol, but it can have up to 3% depending on how long it is brewed.

    Meanwhile, commercial kombucha by law must be under 0.5%.  Of course, if you’ve followed the news over the years, you would have seen many commercial kombucha brands were in fact caught selling kombucha ABOVE the 0.5% limit. But a lot has changed since then. 

    Thanks to the 2010 FDA investigation, the Wholefoods kombucha ban and a Kombucha trade organization being set up... brands have woken up. 

    Not only have they fine tuned their recipes, but also fixed their manufacturing and distribution processes to ensure their products are Below 0.5% alcohol.     


    Now, what about caffeine? 

    Well, there is some caffeine in kombucha, which is not surprising since it uses black or green tea as a starting liquid.  

    But here’s the really cool thing - the Fermentation process reduces the amount of caffeine actually reduces the amount of caffeine. 

    So while an 8 ounce or 240 ml serve of black tea would typically have around 45 mg of caffeine in it, the same serving size of homemade kombucha made from that same tea, will only have roughly 10-15mg.  Or about A 1/4 as much caffeine.  

    And as for commercial kombuchas, they typically have 5-15 mg of caffeine, with some even offering decaf kombucha, which sits at around 1.5 mg.  

    Either way you go, kombucha is a Very Low caffeinated drink.  And thanks to the presence of L-Theanine, a calming amino acid that smooths out caffeine's stimulatory effect, kombucha should be easily tolerated by most people.   


    Okay so what about sugar?  

    If you’ve made kombucha at home before, you’ll know that we need to put a lot of sugar in to fuel the fermentation process. 

    For example, if we’re making a gallon or roughly 4 liters of sweetened tea, we might need to add 1 cup or 200 grams of sugar!  Meaning an 8 ounce or 240 ml serve of the sweetened tea would have 3 teaspoons or 12.5 grams of sugar.  So what’s the deal here?

    Well, the good news is that the yeast in our SCOBY will eat much of this sugar over the course of 1-2 weeks.  This is their fuel!  From studies we’ve seen, 

    Typically a SCOBY will consume between 36% to 84% of the sugar during a 2 week brew cycle.  

    In other words, our 8 ounce or 240 ml serve of kombucha would on average have just 1 teaspoon of sugar left in it.  And of course, The longer it ferments The less sugar it will have. 

    Just note, the sugar content can rise if we decide to flavor it after the initial fermentation with fruit or fruit juices. Of course some of this will also be eaten up by yeast that remains in the kombucha. 

    To put all of this in perspective, a similar serving size of freshly squeezed orange juice would contain 6 teaspoons of sugar or roughly 600% more than kombucha
    Now, what about Commercial kombucha? 

    Well, this is a controversial subject, as several big name brands have been caught Understating their sugar content in recent years.  While others have been found to include lots of Added sugars or have been Added flavourings that may not agree with your gut. 

    To see exactly how much sugar is in all the big brands, plus what other ingredients they flavor their kombucha with, check out our kombucha brands' comparison tool.


    Finally, what about calories?  Well, this all depends on the sugar content, which we have just talked about. 

    But to give you a rough idea, an 8oz or 240 ml serve of unflavored homemade kombuchawith 1 teaspoon of residual sugar would have just 16 calories.  While a similar serve of flavored commercial kombucha might have 25-40 calories.  Not bad. 

    So just to recap - kombucha does contain Some alcohol along with Small amounts of caffeine & sugar. 

    But given the levels are so low, they shouldn’t be anything for a healthy individual to worry about.  And hey, it sure beats drinking a normal alcoholic drink, strong coffee or a sugary soda!

    What are the health benefits of kombucha?

    From Chinese emperors calling it the ‘tea of immortality’ to celebrity doctors hailing it as ultimate cure-all, kombucha must have some serious health benefits.  Right? 

    Well, the answer is “It’s complicated”. 

    So much so, that we actually wrote a separate article going through each potential benefit, one by one, to verify the truth behind it - and you can find the link to that below.  But if you just want the quick facts, here they are…

    • Kombucha does contain healthy ingredients as we looked at before.  From Probiotics, polyphenols & organic acids, it is bubbling with potentially beneficial properties. 
    • And kombucha has been Studied in animals and shown to help with a long list of issues, some of which you can see on the screen now.  And these findings ARE encouraging. 

    Kombucha Benefits in Animal Studies shown to improve:

    Blood sugar levels, liver function, gastrointestinal function, antimicrobial benefits, immune stimulation, antioxidant activity, detoxification and even anti-tumor properties.

    Sadly though, kombucha has not been studied in humans to the same extent.  In fact, kombucha skeptics like to point out that there are No randomized controlled trials focused on the health benefits of kombucha.  What they forget though, is that this is quite common when it comes to functional foods. 

    After all, how many companies or organizations are willing or able to spend big money investigating the health properties of foods they cannot patent? 

    Meanwhile, a 2003 systematic review concluded there was Insufficient clinical evidence to support the many benefits people associate with kombucha.  And although that was nearly 20 years ago, a more recent 2018 systematic review of kombucha’s benefits in human subjects, Also concluded there wasn’t enough evidence.  

    So where do we stand at Essential Stacks? 

    Well, we think it is time for the billion dollar kombucha companies to step up to the plate. 

    After all, thanks to kombucha’s growing popularity - it is actually the fastest growing functional beverage product - they arguably have the money to fund randomized controlled trials.  And most of all, they have the chance to Prove the benefits of kombucha in humans once and for all.  Until then, we remain Cautiously Optimistic.

    What are the potential dangers of kombucha?

    Since kombucha is a fermented and slightly acidic beverage, there are some potential dangers, especially if it is made at home or drunk in excess. 

    Unfortunately, clickbait journalists have blown these dangers out of proportion over the years.  And you might have even seen headlines like ‘could kombucha kill you?’. 

    Well, here at Essential Stacks this type of misreporting and scaremongering frustrates us greatly.  So to set the record straight, we created an article dedicated to looking at which potential dangers are real...and not. 

    In it, we cover everything from potential tooth decay to liver damage and right through to which specific groups of people are most at risk. 

    As you’ll see when you read this article...spoiler alert... we conclude that properly prepared kombucha is Safe for healthy individuals to consume in moderation.

    How much kombucha should I drink?

    So what does moderation look like?  Well, per CDC and FDA guidelines, 4-12 ounces a day - which is roughly 120 to 360 mls - is considered moderate and fine for all healthy individuals. 

    Meanwhile, for those of you with IBS, or who experience some abdominal discomfort when drinking kombucha, limiting yourself to around 4-6 ounces a day - or 120 to 180 mls - can work nicely. 

    Our Conclusion

    So there you go!  Kombucha is pretty interesting right?  Here we have a fermented tea drink that contains all kinds of Potentially beneficial ingredients and not too much of the bad stuff. 

    Of course, how good it is for us humans remains to be clearly shown.  But hopefully in the coming years, human clinical trials will be funded and all the anecdotal reports of amazing health benefits confirmed. 

    In the meantime, we can rest assured that for healthy individuals, properly prepared kombucha IS Safe to consume, and works fantastic as a healthy Alternative to drinking coffee, soda or even alcoholic drinks like beer or wine. 

    And that is enough for me to continue enjoying my daily serving of kombucha!

    Evidence Based

    An evidence hierarchy is followed to ensure conclusions are formed off of the most up-to-date and well-designed studies available. We aim to reference studies conducted within the past five years when possible.

    • Systematic review or meta-analysis of randomized controlled trials
    • Randomized controlled trials
    • Controlled trials without randomization
    • Case-control (retrospective) and cohort (prospective) studies
    • A systematic review of descriptive, qualitative, or mixed-method studies
    • A single descriptive, qualitative, or mixed-method study
    • Studies without controls, case reports, and case series
    • Animal research
    • In vitro research

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