By Yunzhi Qian, PhD student in Nutrition
Nowadays, if you visit a grocery store like Trader Joe’s or Whole Foods, you can easily find rows of kombucha drinks on the shelf. Similarly, multiple cooking bloggers share their homemade kombucha recipes online. What exactly is kombucha, and why is it becoming more and more popular in the US and many Asian countries?
What is Kombucha?
Kombucha is a fermented tea drink that mixes sugar, tea, bacteria, and yeast. It has a tart, effervescent and slightly sweet taste. Added flavors can bring more floral, herbal, or fruity notes to kombucha. To produce kombucha, people use a scoby, which is a symbiotic culture of bacteria and yeast. It looks like a jelly membrane in light tan color, and it can be purchased online in starter kits or cultures.
Kombucha originated in northeast China about 220 B.C, spread to Japan in 414A.D., and later spread to Russia and East Europe through trade routes. It is now one of the fastest-growing products in the functional drink market in the US, with an average growth rate of 40% per year. The popularity of kombucha is driven by touted health benefits such as antioxidants and anti-inflammatory potential, promises of cholesterol reduction and lower blood pressure, reduction of cancer propagation, improvement of the liver and immune system, potential beneficial effect on the gut microbiota, and even advances in technology to bottle the fermented beverages.
With the growing popularity and consumption of kombucha beverages, concerns about its potential risks and safety issues have also increased. For instance, adverse events reported include stomach upset, infections, and allergic reactions in kombucha tea drinkers. Pathogens found in kombucha drinks are mainly due to contamination of raw materials and packages, as well as unsanitary production environments during the fermentation process, which could potentially introduce toxic chemicals.
Current Science on the Benefits of Kombucha
Scientists from the University of Missouri conducted a systematic review in 2018 to evaluate the human health benefit of kombucha. They searched in several different databases as well as the National Institutes of Health (NIH) Research Portfolio Online Reporting Tools and reviewed 310 articles in total. Among the articles they reviewed, only one study examined health benefits of kombucha for humans, and this study did not include a control group of non-kombucha drinkers. However, research on animals and cells suggest that kombucha has beneficial effects on liver and gastrointestinal functions, immune stimulation, detoxification, antioxidant, anti-tumor properties, cardiovascular disease, diabetes, and neurodegenerative diseases. The systematic review reports that the health benefits reported from these studies are likely due to the tea and fermentation products, including glucuronic acid, acetic acid, polyphenols, phenols, and B-complex vitamins that are present in kombucha. Similar findings were published by researchers from Iran, and they also suggested that the claimed beneficial effects of kombucha require further studies to establish.
To support the reported health benefits of kombucha for human health, more studies in humans should be conducted. Furthermore, health and nutrition organizations need to prioritize the creation of more regulations and industry standardization for kombucha production methods, identification of raw materials, and quality control. With a rapidly growing market of kombucha, current regulations are insufficient, and precise safety guidelines are in urgent need.
Peer-edited by Emily Matthew, BS Biology
Picture credit: Wikimedia Commons