Kombucha is a mildly sweet and acidic beverage considered to be a healthy alternative to sugary soda drinks. However, kombucha may contain residual alcohol from the multi-step fermentation process that converts sugar to alcohol. People at greatest risk from low levels of alcohol consumption include: young children, people who are pregnant and their developing babies, those with underlying medical conditions or those taking prescription medications that should not be mixed with alcohol, those who wish to avoid all alcohol for personal or religious beliefs, those with occupational concerns such as drivers, and those with alcohol use disorder.
The purpose of this study was to determine if kombucha available for sale to the public in British Columbia contained levels of alcohol that could cause harm. This is a concern because kombucha that is manufactured and sold as a non-alcoholic beverage is not restricted for purchase as are alcoholic beverages which are only available in liquor stores and other licensed establishments. Kombucha is not labelled nor well known to consumers as potentially containing alcohol. In addition, when kombucha is sold as a raw, living, and unpasteurized beverage there is concern that alcohol may increase over its shelf-life or as a result of temperature abuse. There is currently no information about alcohol levels in kombucha products sold in BC. Other jurisdictions including the US, Australia, and New Zealand have found elevated alcohol in retail products exceeding regulatory values; peer-reviewed publications describe alcohol values in retail products typically ranging from 0.1 to 2% Alcohol By Volume (ABV) with some samples above 3% ABV.
Kombucha alcohol (ethanol) levels were assessed for compliance with BC regulations that define a beverage as liquor (alcoholic) when it contains greater than 1% ABV. Alcohol (or ethanol) levels were detected by headspace gas chromatography mass spectroscopy (HS-GCMS) at the BCIT Natural Health Products Laboratory. This method is extremely sensitive in detecting low levels of alcohol with a detection limit of 0.0002%. In total, 684 samples representing 53 processors were collected during 142 separate visits to a variety of retail, restaurant, processor, farmers' markets, and other BC locations. A broad range of brands and varieties were selected as representative of kombucha products available to consumers at these purchase points, however this may not have included all brands produced or sold in BC. Temperatures of kombucha products at these locations were taken and products were examined for labelling information.
Overall, 31.5% of kombucha samples exceeded BC regulations (i.e., contained levels of alcohol above the regulatory limit of 1% ABV). The highest level was found in BC restaurant kombucha (3.62% ABV). Over 70% of BC processors were identified as having a potential or definite problem with controlling alcohol in their products. In comparison, 33% of kombucha imported into BC from other countries and provinces had potential or definite problems. Precautionary labels about alcohol were found for 54% of brands but often labels were in very small print; three brands displayed statements advising to avoid alcohol during pregnancy with only one including children in the warning. Illegible or unreadable best before dates were found in 5% of products sampled with place of business for the manufacturer poorly described. While 92% of products did advise to keep kombucha refrigerated no product labels explained that it was important to do this to avoid increases in alcohol content; one product advised that contents were under pressure and that the bottle may break if unrefrigerated.
Consumers have a right to know which products have alcohol in them, how much alcohol is present, and what practices may later increase alcohol content. BCCDC recommends that kombucha processors label actual alcohol content and ensure that alcohol content does not increase during a product's shelf-life or during mishandling. Kombucha processors should monitor alcohol in their products and address this hazard as a health concern. BCCDC further recommends that federal authorities require precautionary labelling on products that can contain alcohol to allow consumers to make an informed choice.
 A potential problem was defined as a processor who sometimes (in less than 20% of samples tested) had alcohol over 1% ABV in their kombucha and a definite problem was defined as a processor who often (greater than 20% of samples tested) had alcohol over 1% in their kombucha.