In a recent article, I explained the technicalities of identifying a food as a probiotic. Probiotics are “good” bacteria that benefit our health. And many of these beneficial organisms reside in fermented foods. Yet not all fermented foods can technically be called “probiotics.”

Why? In order for a food to be classified as a probiotic, the microbes it contains must be alive and active and be specifically identified down to subtype or “strain.” And the particular food must have shown a health benefit in randomized controlled trials.

That brought this letter from Amy N. who reads this column in the Santa Cruz Sentinel: “I noticed that you did not include kombucha as one of the possible sources of good bacteria. The kombucha I buy…claims ‘9 Billion Living Probiotics,’ gives their names and quantities, and states that it is a raw kombucha that must be kept refrigerated until consumed. It seems that this checks all the boxes that you listed … but I’d like your opinion.”

As I understand it, Amy, this product may be a valid source of probiotics yet may not, in itself, be a “probiotic.” Bear with me here.

Traditional kombucha (pronounced “kom-BOO-cha”) is boiled black tea fermented with sugar and a mixuture of yeasts and bacteria. Traditional blends of bacteria in kombucha (going back some 2,000 years) have antimicrobial properties that may have been valuable when antibiotics were not available, says Professor Robert Hutkins, author of "Microbiology and Technology of Fermented Foods." But this depends on the particular mix of microbes used.

A handful of studies have shown other health benefits of kombucha, says Hutkins. A randomized-controlled pilot study at Georgetown University Medical Center on 12 people with Type 2 diabetes, for example, showed that daily kombucha consumption helped lower fasting blood sugar levels. Another small study reported that kombucha intake improved some parameters of heart health in obese individuals.

At this point, however, it is not clear if these effects were due to the specific mix of probiotics or from the healthful components inherent in tea.

According to experts at the International Scientific Association for Probiotics and Prebiotics, although kombucha is a fermented food, it may or may not be a probiotic food. That’s because not all formulations of kombucha contain organisms that meet the strict criteria to be called a “probiotic.”

At least two of the microbes in the product you mention are not traditional kombucha bacteria, says Hutkins. So they are not a natural part of the usual baceria and yeast mixture from which kombucha has historically been made. This would be similar to certain yogurt products that have added probiotics, says Hutkins.

In my view, the missing piece for this particular product to be called a probiotic food would be valid clinical studies that show a health benefit for this specific mix of microbes.

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