Is Kombucha Safe?

Recently I met a woman who brews kombucha, and I couldn’t help but ask if she had an extra scoby (symbiotic culture of bacteria and yeast) so I could try my hand at fermenting it myself.


A kombucha scoby is a flat, rubbery disc that floats in a sweetened tea medium. There are a number of organisms in the mix, but for simplicity’s sake, we’ll say that there are two classes of critter involved, various yeast species, which ferment the sugars into alcohol, and various vinegar-forming bacteria, which ferment the alcohol into several organic acids, giving the finished drink an apple cider vinegar pucker and a bunch of interesting components that the average American diet likely doesn’t provide.

Some people praise kombucha as a miracle elixir that cures everything from baldness to arthritis to cancer; others insist it is untested and dangerous.

Look, kombucha had me at “fermented by a scoby.” I just can’t pass up what I’m calling a Microbial Village. That said, I want to understand what risks there are so I can minimize them procedurally, or make an informed decision about whether kombucha is safe to drink.

As far as I can tell, the CDC has documented a total of three (3) hospitalizations linked to kombucha – two in Iowa in 1995, where one woman died, and one in 2009. All three were suffering acidosis, in which the body can no longer regulate its pH and the blood becomes acidic.

Those are real data points, and certainly many more people may have had less serious negative reactions that didn’t require medical attention.

That sounds like a pretty tough indictment of kombucha right there, until you consider that caffeine sends thousands of people to the hospital every year, and has been linked in a handful of deaths, especially from products where caffeine is mixed with other stimulants and can create synergistic effects in the body. Admittedly, caffeine is used daily by the vast majority of the population of the US, but still. You’d think that if kombucha were some sort of silent killer, there would be more than three documented cases of serious injury in 18 years.

And then there’s alcohol, which is really the point of this whole blog. It’s a lot of things, but I can say with clear conviction that I don’t drink for my health. How many hospitalizations result from alcohol on an average Saturday night?

So is kombucha safe? Store bought, I’m going to say yes, in that the product will almost certainly be free of contamination. Will your body love a sudden infusion of live culture enzymes and organic acids? That I can’t tell you. Will it impact how your body uses prescription drugs you may take? I can’t tell you that either. I have a friend who hasn’t eaten grapefruit in years because it was preventing proper absorption of certain of his prescription drugs.

What about home brewed kombucha? Is that safe? That’s a more qualified yes – kombucha can’t be airlocked as it ferments because it needs to breathe, and the home brewer is pouring in cooled, heavily sweetened tea that needs some time to develop a pH adequate to ward off pathogens.

So there’s a risk of contamination, and it’s higher than in most contemporary home brewing scenarios. Interestingly, the scoby usually floats at the surface and will grow to the width of its container, so a mature colony acts a little bit like an oxygen barrier, keeping the fermentable liquid submerged (though this is hardly a perfect seal).

And come on, in nature, a sugary solution will usually become alcohol, and an alcohol solution will usually become vinegar. These are not unique processes. These are the normal pathways of sugar decomposition, seen everywhere that fruits ripen or honeycomb becomes damp.

So, I’m having a good time playing with my new kitchen pet and enjoying the tasty drink it produces. I thoroughly wash my hands before interacting with it, and I monitor it carefully for off odors or signs of surface mold. I’m starting additional scobys as a fallback in case mold or other problems develop, and I was inspired to pour some very old live vinegar dregs into a jar with some bad wine to see if I can’t make a vinegar mother, a very similar complex, producing a similar product.

My kitchen may never be the same!

For another take, here’s a good piece from other experienced fermenters who’ve decided to steer clear of kombucha.

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