I'd like to find out about a fungus called kombucha. I've been told by some alternative health types that it is a beneficial dietary supplement when used as tea. However, I've not been able to find out anything about it. The claims, which I won't go into, seem a bit nebulous — or at least astronomical!


Dear Herbal,

Kombucha is a type of fermented tea, popular 5000 years ago in China and Russia because it was believed to have healing and restorative properties, and popular for the same reasons today, despite mixed evidence of the actual benefits. The beverage, which can taste like either sparkling cider or vinegar depending on how long it has been fermented, is now enjoyed by many people in the East and West. Its purported benefits range from immune system support, to digestive stimulant, to weight loss supplement, to cancer-preventing food — with varying amounts of scientific evidence behind each. But before you sit down to your tea party and drink to good health, it's wise to be aware of the potential health risks involved in consuming kombucha, especially if it has been prepared incorrectly.

Kombucha is typically prepared by combining sugar-sweetened black or green tea with a fungus (called a kombucha mother or scoby) at room temperature for 10 to 14 days. The scoby is a symbiotic colony of yeasts and bacteria bound together by a thin membrane, which can be bought commercially. First, the tea leaves are infused into boiled water at about 165 degrees Fahrenheit and sugar is added. After about ten minutes, the tea leaves are removed, and the symbiotic culture of bacteria and yeast (SCOBY) is added. The mixture is then left to ferment for seven to ten days, covered by a cloth.

The tea varieties, amount of sugar used, and varying fermentation time lengths can affect its chemical composition and hence its health effects. Research (mostly with animal subjects) suggests that specific components of kombucha may provide health benefits, which include:

  • Organic acids (particularly acetic acid), large proteins, and catechins (a type of phenol) that may promote antimicrobial activity
  • Tea polyphenols, ascorbic acid (a form of vitamin C), and DSL (a derivative of glucaric acid) that may lead to antioxidant activity, may have protective effects on the liver, and may even have anticancer effects

Despite the increasing body of evidence, some researchers are still not convinced of these effects; the benefits remain hypotheses due to mixed results across studies. Other benefits attributed to kombucha tea have included relief of arthritis, hair re-growth, increased sex drive, eyesight improvement, and even use as an underarm deodorant or soothing foot soak, but there is not sufficient evidence to validate or refute most of these claims.

Though the brew can be purchased commercially, the low pH of the mixture and the presence of antimicrobial agents in the kombucha mother prevent the survival of most potentially contaminating organisms, making this beverage a popular drink to brew at home. It’s crucial to note that if it’s prepared incorrectly, it can be dangerous. Some warning signs to look out for include:

  • If fermentation continues longer than ten days, the acidity level can become dangerously high.
  • If the acidity level is below 4.2, it is also considered dangerous to consume. If the pH does not rise above 4.2 after a week of fermentation, the batch should be thrown away.
  • If there is any sign of mold growing, the batch should not be consumed.

Even when prepared correctly, the recommended maximum daily amount is four ounces (about half a cup). It’s also good to keep in mind that sometimes the fermentation process creates some alcohol in the kombucha.

Scientists disagree as to the ultimate safety of this fermented tea, as a number of documented cases of severe kombucha toxicity have been linked to both overconsumption and consuming an improperly prepared batch. Symptoms of toxicity can include dizziness, nausea, vomiting, jaundice, neck pain, and allergic reactions. Women who are pregnant or nursing are advised to not drink fermented tea. There have also been noted health risks associated with drinking kombucha for those who are HIV positive. For folks without pre-existing health concerns, consuming no more than the recommended amount a day of the bubblin’ brew is likely safe and may even provide some of the hypothesized health benefits above. Enjoy!


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