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Some data suggest that mixtures of probiotic cultures are more effective than single bacterial strains.

Fred Lum/The Globe and Mail

Does kombucha live up to its health hype?

Q: I’ve heard that kombucha is good for gut health and has other health benefits. Is it something I should drink every day?

Kombucha is trending in the beverage aisle. You’ll find it in umpteen flavours in supermarkets, natural food stores, coffee shops, convenience stores and restaurants.

The fermented drink dates back more than 2,000 years to ancient China, where it was consumed for its energizing and healing properties. Today, its curative claims include enhancing immunity, improving memory, easing arthritis pain, preventing cancer, fighting aging and more.

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Yet, no human studies exist to back up such claims. Here’s what we know – and don’t know – about kombucha.

What is kombucha?

Kombucha is made by fermenting sweetened black or green tea with a SCOBY, an acronym for symbiotic colony of bacteria and yeast. During fermentation, the yeast converts the sugar into ethanol (alcohol) and acetic acid, the compound that gives vinegar its characteristic taste.

The end product is a little fizzy and tastes slightly sweet and slightly sour. You can buy it flavoured with fruit, ginger, rosemary, turmeric, rose petals, elderberries, lemongrass, maple and so on.

Kombucha contains polyphenols, antioxidants that naturally occur in tea and B vitamins. Commercial products contain less than 0.5 per cent alcohol by volume and typically have 30 to 35 calories for every one cup serving, mainly from sugar, considerably less than sugar-sweetened soft drinks.

Is it good for your gut?

It’s kombucha’s probiotic bacteria that are mostly attributed to its purported health benefits. The SCOBY used to make kombucha releases these beneficial bacteria into the tea during fermentation.

Once consumed, probiotic bacteria take up residence in the gut, where they inhibit the growth of illness-causing bacteria and viruses, keep bowel function regular, produce vitamins and maintain a healthy gut microbiota (the diverse community of microbes that live in the large intestine).

Probiotic bacteria provide these benefits if they’re consumed in adequate amounts. It’s not known, however, if kombucha contains enough beneficial bacteria to have probiotic effects; no studies have assessed the drink’s probiotic content, which can vary considerably.

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The mix of probiotic microbes in kombucha depends on the content of the SCOBY, the incubation temperature and how long the product sits on the store shelf. As storage time increases, the amount of live probiotic microbes decreases.

Still, some data suggest that mixtures of probiotic cultures, which are used to make kombucha (and kefir), are more effective than single bacterial strains, possibly because of the greater concentration of probiotics, a broader range of action or synergistic effects of different strains.

The science behind the claims

There’s no evidence that drinking kombucha tea delivers the numerous health benefits promoted on the internet and social media. There are no controlled studies conducted in people drinking kombucha.

Experiments in rodents and petri dishes suggest that kombucha may have anti-diabetes, antimicrobial, antioxidant and liver-protective effects. But you can’t (and shouldn’t) extrapolate these findings to humans.

Is kombucha safe to drink every day?

If you brew your own kombucha, you run the risk of contamination if conditions aren’t sterile. Along with gut-friendly probiotic bacteria, harmful bacteria can flourish during fermentation.

For this reason, it’s recommended that people who have a compromised immune system, elderly people, young children and women who are pregnant or nursing avoid drinking kombucha.

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For other people, though, a research review published earlier this year concluded that drinking 4 ounces of kombucha each day isn’t harmful. Keep kombucha refrigerated at all times, even if the bottle is unopened, to maintain its taste and live probiotics.

Nourish your gut microbiota

Kombucha isn’t the only fermented food that may help shore up the population of friendly gut bacteria. Kefir, kimchi and unpasteurized sauerkraut also contain probiotic microbes.

To keep helpful gut bacteria flourishing, include prebiotics in your daily diet, fibrous, non-digestible carbohydrates that fuel the growth of probiotic bacteria. Excellent sources include Jerusalem artichokes, asparagus, bananas, chicory, dandelion root, garlic, jicama, leeks, onions and whole grains (such as barley, rye and oats).

Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan.

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