Characterization of Vitamin B12 Levels and Compounds in Commercial and Homemade Kombucha

Vitamin B12 is an essential nutrient produced only by certain bacteria and archaea. Kombucha has been promoted as a plant-based source of vitamin B12 to overcome the risk of deficiency associated with vegetarian diets. In this study, the vitamin B12 content of commercial and homemade kombucha was measured using the official Japanese microbiological assay and liquid chromatography tandem mass spectrometry. Only trace amounts of biologically active vitamin B12 were detected in kombucha beverages; in contrast, higher levels were retained within the cellulose-rich microbial culture used for fermentation. Therefore, kombucha cannot be considered a reliable dietary source of vitamin B12.