Scientific Claims
Health claims for kombucha focus on a chemical called glucuronic acetate, a compound that is used by the liver for detoxification. The idea that glucuronic acid is present in kombucha is based on the observation that glucuronic acid conjugates (glucuronic acid + waste chemicals) are increased in the urine after consumption of kombucha.
Early chemical analysis of kombucha brew suggested that glucuronic acid was the key component, and researchers hypothesized that the extra glucuronic acid would assist the liver by supplying more of the substance during detoxification. These analyses were done using gas chromatography to identify the different chemical constituents, but this method relies on having proper chemical standards to match to the unknown chemicals.
A more recent and thorough analysis, outlined in the book in Analysis of Kombucha Ferments by Michael Roussin[19] suggests a different explanation. Roussin reports on an extensive chemical analysis of a variety of commercial and homebrew versions of kombucha, and finds no evidence of glucuronic acid at all. These scientific measurements contradict the earlier studies and conflict with the original hypothesis.
Instead, Roussin discovered that the active component in kombucha is most likely glucaric acid. This compound, also known as D - glucaro -1,4 lactone, helps in the elimination of glucuronic acid conjugates that are produced by the liver. When glucuronic acid conjugates are disposed in the bowel during the elimination process, normal gut bacteria can break up these conjugates using an enzyme called beta-glucuronidase. Glucaric acid is an inhibitor of this bacterial enzyme, so the end result is that the glucuronic acid + waste is properly eliminated the first time, rather than being reabsorbed and detoxified over and over. Thus, glucaric acid probably makes the liver more efficient.
Glucaric acid is commonly found in fruits and vegetables, and is being explored independently as a cancer preventive agent.[20] It has also been discovered that the bacterial beta-glucuronidase enzyme can interfere with proper disposal of a chemotherapeutic agent, and that antibiotics against the gut microbiota can prevent toxicity of some chemotherapy drugs.[21]
Reports of adverse reactions may be related to unsanitary fermentation conditions, leaching of compounds from the fermentation vessels,[22] or "sickly" kombucha cultures that cannot acidify the brew. Cleanliness is important during preparation, and in most cases, the acidity of the fermented drink prevents growth of unwanted contaminants. If a culture becomes contaminated, it will most likely be seen as common mold which is often green, blue or black in color. Often novice brewers will mistake the brownish root filaments on the underside of the culture as a mold contamination when it is seen through the surface of a thinly formed culture.
