By Kathleen M. Zelman, MPH, RDN, LD

Some call it mushroom tea or “elixir of life,” but no matter what you call it, kombucha is one of the hottest trends in health beverages. The fermented tea drink has been around for centuries but recently became popular in the U.S. because of its purported health benefits. Regular drinkers of the tonic claim it aids digestion, sleep, weight loss and detoxification; stimulates the immune system, prevents cancer, stops hair loss, and improves liver function.

What is Kombucha?

Often referred to as mushroom tea, kombucha is not made from mushrooms, but the bacteria and yeast that grow on top of the beverage result in a blob that resembles a mushroom. It is made by adding the bacteria and yeast to sugar and black or green tea and allowing the brew to ferment.

At first taste, kombucha tea tastes somewhat earthy, tart, with a little effervescence and a vinegar-like smell – not so pleasing to the taste buds. To make the tea more palatable, juice is added to the base brew. But if you look a little closer, you notice little floating bits of bacteria in the unpasteurized beverage.

The fermented beverages are high in acid and contain sugar, vinegar, B vitamins, antioxidants (from the tea), trace amounts of alcohol (a natural consequence of fermentation), and other chemical compounds. One 16-ounce bottle contains about 60 calories, which is less than a soft drink.

Home-brewed varieties start by either purchasing the ‘kombucha mothers’ starter or by using a starter sample from an existing culture to grow a new colony of bacteria and yeast that ferments in a clean jar for 7-14 days. Some brands are pasteurized to kill potential pathogens; other brands and most home brews are drunk raw or unpasteurized.

Safety Record

Some experts warn about the dangers of home-brewed and unpasteurized kombucha prepared in nonsterile conditions and the risk for unhealthy bacteria getting into the tea.

“If you want to drink kombucha, a safer bet is to go for one that is commercially prepared and pasteurized,” says Janet Helm, MS, RD, a Chicago nutritionist and author of Nutrition Unplugged blog.

There have been reports of adverse effects from drinking the tea, ranging from upset stomach to toxic reactions and metabolic acidosis (excessive acid buildup in the body). The FDA cautions that home-brewed versions are at high risk of contamination. In 1995, the CDC issued a report linking kombucha with the illness of a woman suffering from metabolic acidosis.

 Alcohol Content

Unpasteurized kombucha, like overfermented fruit, can ferment in the bottle unless it is refrigerated, bringing its alcohol content to the level of some beers. Pasteurizing the beverage makes it safer and reduces the likelihood of increasing alcohol levels. But most kombucha drinkers want the natural, unprocessed beverage.

In June 2010, Whole Foods pulled kombucha from store shelves across the country because of concerns about the fluctuating alcohol content beyond the legal limit of 0.5 percent.  Since then, suppliers have met their standards and are back on the shelves.

Benefits of kombucha tea are primarily based on personal reports and a few animal studies. There are no clinical trials or sound scientific evidence to substantiate the numerous claims. That is not to say there are not any benefits from drinking the tea; it simply means there is no evidence that proves the benefits it claims.

Kombucha’s popularity is in part due to the probiotic content of good-for-you bacteria that studies show can benefit digestion and boost immunity. In order to maintain the probiotic benefits, the tea must not be pasteurized, which also increases the risk of contamination.

Helm says yogurt is a better choice if you want to boost your probiotics because it also contains a wealth of healthy nutrients like protein, calcium, and potassium. And, often it is fortified with vitamin D.

Drinking 4 ounces daily of commercially available pasteurized kombucha tea is generally considered safe for healthy people. However, it would be prudent for pregnant women, elderly people, children, and anyone with a compromised immune system to avoid it.

Bottom Line

The claims are greater than the science can prove and the safety factors require careful selection. Drink it in moderation if you enjoy it but be warned, it may be an acquired taste. And don’t drink it because of the overstated benefits.

“Kombucha is not a cure-all or magical elixir but it does have some beneficial bugs similar to yogurt, kefir, or other probiotic drinks… don’t drink it because of the over-the-top claims, but only if you like it,” Helm says.