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Choosing kombucha

Reviewed by our expert panel
Choosing kombucha

Everyone’s drinking this fermented tea, but there’s little science, so far, to back health claims. Dietitian Katrina Pace explains how to make informed choices.

Kombucha sales in New Zealand are growing rapidly, as evidenced by the explosion of products in our supermarkets. It’s seen as a healthy and tasty alternative to fizzy drinks or alcohol, but how healthy is it really? We investigate what to think about when buying kombucha.

Why buy kombucha

Apart from being another drink option, is there any other reason to buy kombucha?

Many people choose to drink kombucha because of perceived health benefits.

Kombucha is a fermented drink made from black tea, sugar and a starter culture, called a SCOBY, which stands for symbiotic culture of bacteria and yeast. Fermented over seven to 10 days, the bacteria and yeasts feed on the sugar, growing in number and making a sour, fizzy drink. It’s these bacteria and yeasts that make kombucha such a popular functional food (with extra health benefits). The species of bacteria and yeasts, and the amount present in kombucha, are thought to be beneficial for our gut, which then has the potential to affect other areas of our health.

Kombucha also contains antioxidant polyphenols from the tea, several vitamins and minerals and other organic compounds that may be important in maintaining health.
One problem, however, is the clinical effects of kombucha have not been widely studied in humans.

A recent systematic review identified there are no published controlled studies investigating the effects of kombucha on human health, although there are case reports.

What’s in -store bought kombucha?

It may be convenient to buy from the ever-expanding range of kombucha found at the supermarket or dairy but you can easily make kombucha at home.

All kombucha is made with tea, sugar, water and a kombucha starter. Other common ingredients found in bought kombucha include:

sweeteners: stevia (steviol glycosides), erythritol
fruit juice
carbon dioxide.

When tea, sugar and water are combined and left to ferment, the bacterial and yeast products grow and will eventually form a visible colony, the SCOBY. The fermented liquid and the SCOBY can then be added to more tea, water and sugar to produce more kombucha.

Sugar is an essential part of producing kombucha as, without it, the bacteria can’t grow. However, during fermentation, the amount of sugar in the liquid reduces as it’s eaten by the bacteria, making the final product low in sugar and sour to taste. The amount of sugar left in kombucha depends on how long it’s fermented for. Most bought kombucha contains 1g-5g sugar per 100ml. This is less than other fizzy drinks, such as organic ginger beer or Coca-Cola, with around 10g sugar per 100ml.

What are sweeteners doing in kombucha?

Many fermented foods have a strong sour flavour (think sour cream, yoghurt, pickles) and kombucha is no different. Many people aren’t used to, or don’t want, a sour drink, so manufacturers may add a sweetener to make the kombucha more palatable. Alternatively, they may not leave it as long to ferment, so more sugar (and sweetness) remains. What isn’t clear is how added sweeteners may affect the bacteria and yeast growing in kombucha. Stevia has antimicrobial properties that may affect the final product but, as yet, there is no research to confirm its effect as an additive in kombucha.

Fruit juices can be added as flavour or for sweetness, and carbon dioxide for a reliable amount of fizz, in the final product. Probiotics may be added to enhance the amount of probiotics in the kombucha.

What about he alcohol in kombucha?

Fermentation produces not only the fizz in kombucha but alcohol too. The longer the fermentation, the more alcohol tends to be produced. Researchers investigating US store-bought kombucha found the 18 products they analysed contained 1.1 per cent to 2.0 per cent alcohol by volume (ABV). In New Zealand, drinks with greater than 0.5 per cent ABV are required to be labelled as alcoholic beverages. How the US products compare with kombucha made in New Zealand isn’t known.

Research has also shown that kombucha stored in the fridge and consumed as soon as possible has a lower alcohol content.

Unlabelled alcohol in kombucha is one reason we don’t recommend drinking kombucha if you’re pregnant or breastfeeding.

First published: Mar 2019

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