Kombucha's Health Benefits: Which Claims Are True?

Of all the hot-right-now, old-as-the-hills fermented foods that are being touted as cure-alls for an array of specific medical problems, kombucha tops Sandor Katz's list.

The author of The Art of Fermentation told me that he's seen claims that kombucha will "prevent your hair from going gray, will prevent you from getting cancer, will cure everything."

And kombucha is also more popular in mainstream US grocery stores, convenience stores, and restaurants than ever before. In March 2016, the market research company Mintel released their prediction that 51% of US adults aged 25 to 34 already drink kombucha, and attributed some of its recent hype to a "buzz from lifestyle food bloggers [that's] creating awareness among consumers [who] don’t lean toward the extremes of a healthy lifestyle, but are open to something new."

(For a sense of kombucha's reach: I visited my 90-year-old grandparents in Michigan this past weekend and even they had a bottle of kombucha in their refrigerator. For full disclosure: I love to drink kombucha and am currently brewing my own.)

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But just what role does kombucha play in a so-called "healthy lifestyle"? Back in 1997, the American Nutrition Association listed some of the wide-ranging health benefits attributed to "kombucha tea," from lengthening lifespan to aiding in the treatment of psoriasis and limb pain to AIDS to restoring hair color.

And, more recently, in the introduction to their book Kombucha! The Amazing Probiotic Tea That Cleanses, Heals, Energizes, and Detoxifies, Eric and Jessica Childs of Kombucha Brooklyn refer to kombucha as "an ancient elixir that is excellent for health and well-being in our modern world" that "detoxifies the liver and blood, [...] provides a crash-proof energy boost, [...] focuses the mind, [...] settles digestion, and [...] streamlines a variety of inefficiencies in the body." People drink kombucha, they say, "because it makes their lives better."

The elegantly beautiful keep a bottle nearby to help them stay young and gorgeous. Health experts laud kombucha’s natural detoxifying properties, including it in their prescription for optimum health. Whatever your reason for trying kombucha, you will be amazed by how easy it is to make and how effective it is in optimizing your health.

Can we believe it? "There's all sorts of unscrupulous marketing and people making unsubstantiated claims," Katz told me, and this makes it easy for us skeptics to dismiss the health assertions altogether. Yet "we have to be careful not to throw away the baby with the bath water," he warned. Probiotic foods can contribute to an overall restoration of diversity in the gut, Katz said, but "what benefit that has is very vague and general" even if we do know the bacteria in our intestines are integral to many different physiological processes.

"As much as I love kombucha (and sauerkraut and kefir and many other ferments), it is not reasonable to expect any single food or beverage to cure specific diseases," he writes in the forward to The Big Book of Kombucha: Brewing, Flavoring, and Enjoying the Health Benefits of Fermented Tea by Hannah Crum and Alex LaGory.

So is kombucha the panacea many Americans have been missing for hundreds of years, or is the latest beverage to earn valuable grocery store real estate and marketing dollars? Turns out, kombucha is a little bit of both.

We're breaking down what we know to be true from what is less certain:

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What we know:

• The practice of drinking and brewing kombucha is ancient. Kombucha is thought to have originated in Manchuria circa 220 B.C.E—which means that people have been drinking it for quite some time (and that there is a lengthy anecdotal history of health benefits).
• Kombucha is fermented tea. To make kombucha, a symbiotic colony of bacteria and yeast (SCOBY) is introduced to sweetened black or green tea. The yeast breaks down the sugar into carbon dioxide and alcohol, and then the bacteria converts that alcohol into acetic acid, which provides the drink with its vinegary sharpness. Since the bacteria doesn't use all of the alcohol, kombucha will always contain trace amounts of it. (In 2010, Whole Foods pulled all kombucha products off their shelves when the Maine Department of Agriculture discovered their stock to contain more than five times the amount of alcohol legally permitted for non-alcoholic drinks.)
• Raw, unpasteurized kombucha is full of probiotics (live bacteria and yeast that naturally occur in the body, or are very similar to those that do)—and probiotic supplements have been shown to bolster the immune system and aid in digestive health. “The only reason anybody would drink kombucha, outside of the fact that they enjoy the taste of it, is that it has good bacteria, which could potentially translate into a healthier microflora in our own intestines," Jennifer McDaniel of Academy of Nutrition and Dietetics told NBC News. What's more, the probiotic benefits are not unique to kombucha—eating yogurt, sauerkraut, kimchi, or kefir, for example, will also do service to your gut ecosystem.

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• Kombucha also contains sugar, B vitamins, and, by way of tea, antioxidants—though a 2014 study found the antioxidants in kombucha to be higher than in unfermented tea.
• And, though rare, drinking—and, especially, brewing—kombucha comes with risks. Because the pasteurization of kombucha kills off the good bacteria along with the bad, only unpasteurized brews contain the live cultures lauded for their digestive, immunity-boosting benefits. But consuming unpasteurized kombucha, especially when it's produced in a non-sterile setting, like a home kitchen, rather than in the facilities of a reputable company, carries the risk of toxic encounters with harmful microorganisms.
  
  As an alternative, some nutritionists and health professionals recommend other probiotic-rich foods and beverages that can confer similar benefits at lower risk. And because kombucha falls into the category of "folk medicines, herbal remedies, and dietary supplements," it is not regularly evaluated by the USDA or FDA. Kombucha is not recommended to be consumed in excess (no surprise there), and it's also not advised for pregnant women, children, or those with compromised immune systems.
• Kombucha has changed many peoples' lives. You don't have to look hard or far for case studies and anecdotes that attribute great changes in well-being to kombucha consumption. In the introduction to the The Big Book of Kombucha—the same book that publicizes Sandor Katz's message that kombucha cannot cure specific diseases—the owners of Kombucha Kamp tell the story of their love affair with kombucha, which, they say, changed "the demands" of their bodies:

We found ourselves craving less of the over-processed junk food we had been accustomed to eating and more of the nourishing, nutrient-dense food that better supported our individual well-being. Over time, we came to live by our simple mantra, 'trust your gut.'

To read these kombucha success stories is to not think of the beverage as a beverage, but as a way of eating—and even, of living.

What we don't know:

• The exact composition of any one brew—because it changes between batches. Kombucha is a source of probiotics, but the exact composition varies: " The amount and diversity of these organisms present in the bottled beverage can vary widely, depending on brand and production method," reports the International Food Information Council Foundation.
• Any scientifically proven health benefits to humans (rather than lab models). A June 2014 review of the microbiology, composition, fermentation, beneficial effects, toxicity, and tea fungus of kombucha in the Comprehensive Reviews in Food Science and Food Safety concluded that "[t]here has been no evidence published to date on the biological activities of kombucha in human trials. All the biological activities have been investigated using animal experimental models." That none of the scientific studies cited in Authority Nutrition's article on 8 Evidence-Based Health Benefits of Kombucha Tea (that kombucha kills harmful bacteria, or reduces live toxicity, or improves LDL and HDL levels) were conducted on humans is not to say that randomized trials of humans subjects would not yield evidence to support this data, but that there is no way to declare it with certainty.

The konclusion*:

The probiotics in raw, unpasteurized kombucha, which you can also find in yogurt, kimchi, and other fermented foods and beverages, may confer some health benefits. Other claims—that kombucha cures cancer, or fights free radicals, or detoxifies the body—have not been proven in humans, though you yourself might find the anecdotal evidence of various individuals convincing.

So drink kombucha—in moderation, and prepared as safely as possible—if it makes you feel good and/or you enjoy its taste (sharp and fizzy, with a vinegary sweetness), but know that a doctor will not prescribe it as medicine.

"The bottom line," writes Patti Neighmond for NPR's The Salt, "is that we know very little about kombucha and how it may affect health.”

*Please forgive me.

How do you feel about kombucha? And when did you first try it? Tell us in the comments below.