An Australian study has found that many types of kombucha and kefir contain alcohol.

The fermented "soft" drinks have soared in popularity in recent years amongst the health-conscious and those who want to cut down on their drinking.

However, researchers from Victoria's Department of Health and Human Services found that some bottles of kombucha contain as much alcohol as half a light beer.

They are calling on manufacturers to disclose the alcohol content of their products on the labels.

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Next time you decide you want a night off the sauce and opt for the virtuous choice of kombucha over a glass of wine, you may want to think again — especially if you're driving or pregnant.

Fermented drinks like kombucha and kefir aren't actually alcohol-free, and drinking a lot of them could even leave you over the drunk driving limit, an Australian study conducted by Victoria's Department of Health and Human Services on behalf of Food Standards Australia and New Zealand has found.

Alongside sauerkraut and kimchi, gut-friendly "soft" drinks kombucha (made by fermenting tea) and kefir (cultured, fermented milk) have soared in popularity amongst the health-conscious in recent years.

Read more: Everything you need to know about kombucha — the trendy 'health' drink that could be good for your gut

And as more young people choose not to drink alcohol, many sober-curious or teetotal people are turning to the likes of kombucha in the place of booze.

However, due to the fermentation process involved in creating kombucha and kefir, alcohol is formed as a by-product. The researchers wanted to find out whether the amount was enough to breach the Australia New Zealand Food Standards Code by containing undeclared alcohol.

They pointed out that if these beverages did contain more alcohol than most people think, it could pose concerns for pregnant women, designated drivers, recovering alcoholics, and those who are underage.

Some fermented drinks contain as much alcohol as half a light beer

Whilst it was previously thought that the alcohol produced in fermenting drinks was such a small amount it was negligible, the new study found that some bottles of kombucha contain as much alcohol as half a light beer.

Researchers assessed 239 drink samples from across five areas of Australia, the majority of which were kombucha (132), followed by water-based kefir (43), and dairy-based kefir (7). The remaining 57 drinks sampled came under "other," and included the likes of ginger beer.

The alcohol content in all the drinks was measured, and they found that:

22.9% of the kombucha samples were more than 1.15% ABV, while 41.9% were between 0.5% and 1.15%, and the remaining were less than 0.5%.

36.7% of the water-based kefir samples were more than 1.15% ABV, and the same percentage fell between 0.5% and 1.15%.

All the dairy-based kefir samples were under 0.5% ABV.

68.6% of the "other" drinks tested were under 0.5% ABV.

To put this into context, the average beer is around 4.5% ABV, but some are less, so not much more than some kombuchas.

In certain places, drinks that are over 1.15% ABV are classified as liquor, meaning you need a licence to sell them and proof of age to purchase them.

In the UK, for example, drinks can only be deemed "alcohol-free" if they're under 0.05% ABV, according to DrinkAware. Beverages that are between 0.05% and 1.15% are classed as "low-alcohol," and anything above that is simply alcohol.

The researchers pointed out that the alcohol content in fermented drinks has the potential to rise the longer it is before the beverage is consumed.

They found that the amount of alcohol in the drinks varied depending on what other ingredients had been added and the process by which the effervescence had been created.

The Food Standards committee is now calling on manufacturers to be more responsible in how they label their drinks.

Kombucha and kefir drinks may not all be as healthy as people think

"When people think they are buying a soft drink that has no alcohol that is what they should get," Margaret Allman-Farinelli, Professor of Dietetics at the University of Sydney, told The Sydney Morning Herald.

"With respect to cancer risk, the finding is there is no safe level of alcohol intake. The same applies for damage to the fetus during pregnancy."

High in probiotics, kombucha has been lauded as a health drink that will improve your digestion, boost energy levels, and aid your overall wellbeing.

However, not all forms of the the fizzy, fermented tea are as virtuous as you might think — some are high in sugar, and drinking too much can leave you bloated and cause bowel problems, as Insider's Gabby Landsverk previously reported.

That being said, studies have linked kombucha consumption with killing harmful microorganisms, improving liver and kidney function, and weight loss.

If you enjoy fermented drinks, you don't need to stop consuming them — it just might be worth factoring in that a buch or two on a Friday evening may mean you're not totally sober.

Read more:

6 potential health risks of drinking kombucha, from accidental tipsiness to uncomfortable bloating

I lost 35 pounds in 6 months without going on a diet, and it taught me 7 lessons about eating for healthy fat loss

How calorie-counting actually helped me develop a healthier relationship with food