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Kombucha health benefits: Here’s what science says

Coconut oil, acaí berries, kimchi, matcha, spelt: All are trendy health foods that are actually not new at all — just like kombucha, the hotter-than-ever fermented-tea beverage with a truly ancient history.

“It’s a tradition that dates back more than 2000 years,” Dr. William Li, author of Eat to Beat Disease, tells Yahoo Lifestyle.

Kombucha, a fizzy drink created by fermenting tea (most commonly black or green) and sugar with a symbiotic culture of bacteria and yeast known as SCOBY, was first used for its healing properties in East Asia — initially in China, where it was beloved for its “energizing effects,” according to a comprehensive new study coauthored by epidemiologist Julie Kapp, Kombucha: a systematic review of the empirical evidence of human health benefit, published in the Annals of Epidemiology in February.

The elixir then made its way to Japan, before catching on in Russia, Germany, France, North Africa, Italy and, finally, Switzerland, when 1960s researchers noted it had health benefits similar to those of yogurt because it contains probiotics, which introduce new bacteria into the gut microbiome.

“This helps to increase the diversity and enrich healthy bacteria populations in your gut, which can have many beneficial effects ranging from improved immunity and lowered inflammation,” Li explains.

Today, in the U.S., you’ll not only find kombucha at any health-food store, but sharing shelf space with juices and sodas in an increasing number of regular delis and mini-marts. In fact, a recent MarketsandMarkets report showed sales of kombucha are expected to grow by 25 percent every year through 2020 to a value of $1.8 billion.

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But what scientific evidence do we actually have about the purported health benefits of drinking the bubbly, vinegar-like brew? Some. But less than you might believe, based on the hype surrounding kombucha.

“The health benefits have been touted, but not studied in a well-controlled environment,” Jo Ann Hattner, a San Francisco-based registered dietician and nutritionist and co-author of Gut Insight: Probiotics and Prebiotics for Digestive Health and Wellbeing, tells Yahoo Lifestyle. We do know that the drink contains probiotics, Hattner says, noting, “I have clients who drink kombucha because they want to enjoy a fermented drink and they want the live fungi and bacteria for their gut health. These clients are often looking for a fermented, dairy-free drink.”

But beyond the knowledge about probiotics — confirmed in lab tests of kombucha’s properties — we don’t have many studies to go on. That’s because the body of scientific evidence we do have is based on largely on animal testing, which leaves some experts skeptical.

“Besides having different biology, humans have a lot of distinct environmental and behavioral factors, so it’s important to conduct the human studies,” Kapp tells Yahoo Lifestyle, adding that we should give such animal-based studies “not too much” weight in assessing kombucha’s benefits. “We need to be cautious about expecting animal study results to predict humans’ real-world results.”

Trendy kombucha can increasingly be found served on tap, such as at this health food store in Huntington Beach, Calif. (Photo: Kevin Sullivan/Digital First Media/Orange County Register via Getty Images)

There has been one human-based kombucha study, however, albeit small (and with no control group), which Kapp finds compelling. It has to do with blood-sugar levels, which is why some believe it could be an important tool in managing Type-2 Diabetes.

The study, from 2002, looked at 24 individuals with non-insulin dependent diabetes mellitus, and found that, after 90 days of consuming just two liters of kombucha daily, subjects had a “significant reduction” of blood sugar levels, which remained stable for at least a month afterward. “The lead author’s dissertation also describes improvements associated with the same intervention in individuals with mild hypertension or diverse medical problems,” noted Kapp in her scientific review. And while she tells Yahoo Lifestyle that the study “does not provide enough evidence to endorse kombucha,” it does “offer some leads for further research.”

Here’s a look at what else we know — and don’t exactly know — about the purported health benefits of kombucha:

GUT HEALTH

Because the fermentation process makes a drink that’s rich in probiotics, many believe that drinking kombucha is good for your gut health, providing a healthy blend of bacteria to absorb nutrition and fight off infection in a way that’s similar to that of fermented kimchi, sauerkraut or yogurt.

There was, in fact, one scientific analysis, in 2014, that identified the specific strains of kombucha’s bacteria. It found significant amounts of Gluconacetobacter (which merely creates cellulose) and Zygosaccharomyces, which merely create cellulose (a complex carbohydrate) and offer flavor, respectively. But it also found Lactobacillus, which is found in yogurt, and believed to possibly reduce cholesterol, help with Irritable Bowel Syndrome symptoms, and prevent vaginal infections.

Li — who is the medical director of the Angiogenesis Foundation, dedicated to “disrupting disease through angiogenesis,” the body’s process of growing blood vessels, touts fermentation and probiotics as good ways to fend off disease.

“Fermented foods and probiotics both add healthy bacteria to enhance your microbiome health defense system in the gut,” Li explains. “Many serious health conditions now are tied to abnormalities of the microbiome, including obesity, metabolic syndrome, type 2 diabetes, and systemic inflammation. When beneficial bacteria are absent, the immune system’s ability to detect and fight cancer cells is lessened. Overgrowth of unhealthy bacteria, on the other hand, can result in the release of harmful metabolites that can cause inflammation, which can fuel the growth of cancer cells.”

ANTIOXODANT POWERS

Li, a big proponent of green tea, notes that kombucha may share some of its beneficiary properties.

“The prebiotic action of green tea increases our gut’s population of healthy bacteria that produce short chain fatty acids. These fragments are produced as metabolites of gut bacteria and they have anti-inflammatory effects in the intestine,” he says.

Further, Li notes, green tea activates the body’s regenerative capabilities. “A study from Korea showed that consuming four cups green tea daily increased circulating stem cells by 43 percent over two weeks, and this was accompanied by improved blood vessel dilation by 29 percent.” Green tea also can calm the immune system, he says, noting there’s been evidence showing that drinking it can decrease symptoms in women with the autoimmune disease lupus.

CANCER PREVENTION

The anti-cancer potential for kombucha most likely come from the anti-angiogenic (cancer starving) properties of tea, Li explains. “Green tea contains a polyphenol called EGCG, which can starve cancers by cutting off their blood supply (anti-angiogenesis). Studies out of Vanderbilt University involving 69,700 people that shown that drinking two to three cups of green tea a day is associated with a 44 percent reduced risk of developing colon cancer.” Those are great reasons to opt for kombucha that’s been brewed from green tea, rather than black or red.

Further, he posits that an enriched microbiome may also better protect the body against cancer by boosting the immune system. But, he notes, “More research is needed, however, before kombucha can be regarded as having anti-cancer properties.”

Adds Karr, “There have not been human clinical trials yet testing whether kombucha can prevent cancer. At this point, kombucha health claims for humans and cancer are speculative or anecdotal. Nevertheless, there is a lot of science currently focused on probiotics and the microbiome, so it is an exciting time to study this area.”

Bottom line: Kombucha, although lacking a big body of scientific evidence in its favor, is refreshing, backed by centuries of use, and good for your gut.

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