Does fermented drink kombucha actually have health benefits?
It's murky brown, laced with fermented mushroom and tastes like slightly sweet, effervescent vinegar, but that hasn't stopped kombucha becoming the latest drink of choice for health-conscious Hongkongers.
Kombucha (pronounced kom-boo-cha) is produced by combining sweetened tea with "Scoby" - symbiotic colony of bacteria and yeast - which looks like a flat beige mushroom, and leaving it in the back of a cupboard for a week or two. It has been quietly consumed for centuries in Russia and China, but only recently has its popularity soared.
While it might not sound great, it tastes better you think, particularly when brewed with flavour combinations like lemon grass and ginger or pomegranate and passion fruit.
Plus, it's all in the name of good health - or at least that's the belief. Kombucha devotees make many miraculous claims about the elixir, from preventing cancer, stimulating the immune system, improving digestion and liver function as well as bringing about hormonal balance.
There's only one problem: there is no medical evidence supporting these claims. So far, studies on kombucha consumption have been on rats, not humans.
A study published in Food Chemical Toxicology looked at the effect of consuming kombucha on rats that had been induced into diabetes by a contaminant called alloxan. In the study, it was found that kombucha consumption effectively restored the alloxan-induced changes in the body. While black tea had the same effect, kombucha was found to be "more efficient".
In an earlier study, published in Food & Function in 2010, researchers fed kombucha to mice with stomach ulcers. They found that black tea fermented for four days with a kombucha culture was as effective in treating the ulcers as the control medication, omeprazole. (Again, researchers also found regular black tea was effective, although, once again, not as effective as kombucha.)
Other studies on kombucha-drinking rats have found improvements from a bolstered immune system, improved liver and kidney function as well as repair to damage caused by environmental pollutants.
"What you can't infer from [studies on rats] is that kombucha is good for this disorder or this condition, but what you can say is there are certain compounds in kombucha that have certain benefits - but it's quite an extrapolated inference," says Brian Leung, a board licensed naturopathic doctor, chiropractor and kinesiologist at the Integrated Medicine Institute in Central.
Leung hails from the United States, where the fermented drink has enjoyed popularity over the past 10 years, and considers himself a kombucha drinker. He believes in its health benefits, but is under no illusions.
"A lot of the health benefits you see from drinking kombucha are related to the presence of green tea and black tea - for which the benefits are already well known."
"The bacteria in the yeast also has a synergistic effect with the compounds in the tea, known to create saccharic acid - a compound of sugars with acid - which has been shown to be anti-cancer as well as high in anti-oxidants, which protects your liver. The fermentation process of black tea will also improve the antioxidant rate.
More precisely, the bacterial genus known as Gluconacetobacter, found in 85 per cent of samples tested in one study kombucha published in Food Microbiology last April, has shown a strong ability to produce glucaric acid or saccharic acid. The acid is known to have anti-cancer and detoxifying properties; humans produce small amounts of the acid, but it's also found in fruits, particularly citrus fruits, vegetables like broccoli and kale and legumes.
An improvement in gut health - the most touted benefit of the brew - is unsupported, warns Leung. "In our clinical practice we don't recommend it [for improved gut health] and you won't find a lot of practitioners in Hong Kong that would."
As a general food group however, "fermented foods are very beneficial in terms of probiotics, which are heavily studied…but kombucha should not be seen as a replacement to your regular probiotic because it doesn't contain Lactobacillus or Saccharomyces boulardii (commonly found in regular probiotics)."
As a "general health drink", he says, "it has benefits in terms of overall wellness". He also acknowledges that some of the beneficial bacteria present in the drink would certainly affect that sphere of the gut, "but there's really no studies to prove that yet," he adds.
And if you have a compromised immune system or suffer from lactic acidosis - when your body is in a very acidic state - stay away from it completely.
But naturopath Louise Buckley has a different, more personal view of kombucha: "Just because science hasn't worked out why, doesn't mean it's not beneficial," she says. The practising naturopath has been teaching the benefit of fermented foods for the last three years and has experienced vast gains from her kombucha brew.
"Personally, I can now eat wheat and dairy - my digestive issues, bacterial issues, energy and hormone issues has turned itself around and I credit a large part of that with changing my gut bacteria, which is contributed by drinking kombucha."
Scientifically backed or not, Hongkongers like Buckley are making their own kombucha brew with fervour. Her Facebook group Fermenting Hong Kong has grown to more than 700 members since it started 18 months ago. She conducts brewing courses every two months and has even written a book about all things kombucha.
Time-strapped locals are also flocking to buy the fermented fizz. There are three reputable, well known kombucha producers in Hong Kong who together make about 60 litres a week: Taboocha, Anything But Salads and Green Vitamin.
Hong Kong organic eatery, Mana, has been selling an exclusive blend from Taboocha, made of chamomile, green tea and lemon grass since the beginning of the year. Despite costing a hefty HK$60 a bottle, it sells about 40 bottles a week. "Right now we are running out before the next delivery - we are about to up production," says co-founder Christian CGM.
"The fact that kombucha has been around as long as it has and continues to be used says a lot more to me than any scientific studies," says Buckley. "The benefit of bacteria is well researched, as is the human microbiome - it's just a matter of time before the science catches up."
WHERE TO GET IT
92 Wellington Street, Central
Anything But Salads
Shop B, G/F, 14 Tai Ping Shan Street, Sheung Wan
Just Green Convenience Store
Central, Soho, Wan Chai, Lamma Island, Discovery Bay
72 Third Street, G/F Shop K, Fook Moon Building, Sai Ying Pun
To join the fermenting community, visit facebook.com/groups/fermentinghk/
To take part in a Kombucha brewing course sign up at Loula Natural
loulanatural.com or Sesame Kitchen sesamekitchen.com