Importance of Topic to Practice
There has been increasing interest in kombucha tea due to its purported health benefits, including boosting antioxidant and anti-inflammatory potential, alleviating or improving arthritis symptoms, reducing blood pressure, promoting healthy gastrointestinal functions, improving resistance against cancer and improving immunity (1-3).
Kombucha tea is a fermented drink made with sugar, black tea, yeast and bacteria (1). According to historical reports, it was first made in East Asia as early as 220 BC. It was brought to Japan in about 400 AD and, due to the expansion of trade routes, found its way to Russia, Eastern Europe and eventually into Germany in the early 1900s and is now widely consumed. It has a similar taste to apple cider. More research is required to establish its safety and biological effects on humans.
What is kombucha tea?
Kombucha tea is traditionally a sweetened black tea that is fermented with a symbiotic culture of bacteria (acetic acid bacteria) and yeast (osmophilic) (SCOBY), which is also called a “tea fungus” (1,3). It can be commercially or locally (home) prepared (1,3). While green, oolong, red and white tea can also be used, black tea is usually used to make kombucha tea (1). Typically, the fermentation time is seven to 12 days at room temperature (3,4). The biochemical properties of kombucha tea can vary based on the original recipe and the fermentation microbes, resulting in a final composition that can vary from drink to drink.
Are there safety and/or health concerns?
Locally prepared or homemade, kombucha tea can have safety concerns compared to commercially prepared teas due to the leaching of chemical contaminants from the fermentation pots or packaging material and/or from the types of bacteria and yeast (5). For example, kombucha tea was traditionally made in lead-glazed ceramic pots, which could cause lead or other toxic chemical poisoning (1). The high acid content of the drink can cause the metal to leach into the drink during the homebrewing process (1-3). Therefore, it is important to ferment it in a safe, nonmetallic container (1-3,). As well, if prepared with unclean or non-sanitized utensils or in non-sterile conditions, there is a risk that pathogenic microorganisms could contaminate the brew at various steps in the preparation of the kombucha tea (i.e. brewing, filtering, fermenting) (2,3,5,6). However, if prepared following an established recipe and with proper brewing methods, including using clean and sanitary equipment, risk may be minimized (1,6). Toxicity reports exist, including reports of dizziness, nausea, unexplained severe illness, allergic reactions, lactic acidosis, liver toxicity but are rare and isolated and usually occur when kombucha is consumed in large amounts (more than 125 mL/1/2 cup/day) (1,3,7). In a 2019 food safety survey, the Canadian Food Inspection Agency (CFIA) tested 60 commercially-produced kombucha samples from across retail locations in 11 cities across Canada and found no contamination with Salmonella spp., generic E.coli or E.coli O157, B. cereus or S.aureus, suggesting that they were produced under sanitary conditions (8). The CFIA concluded that commercial fermented teas are safe for consumption.
There is often confusion around the health benefits and health implications of consuming kombucha tea (1,3). While it has been claimed that kombucha tea exhibits antimicrobial, antioxidant and anticarcinogenic properties, there is a lack of human clinical evidence to support these claims (1,3). To date, the suggested health-related properties of kombucha tea have only been studied in animal and cell cultures (1,3). The consumption of kombucha tea is not recommended for particular subgroups of the population, including those with compromised immunity (i.e. HIV/AIDS) and pregnant and lactating women, especially if homebrewed (2,3). Regarding children, kombucha tea can contain alcohol (2) and the evidence on dose, safety and health risks of kombucha tea specific to children is lacking.
Relevant Basic Information
What is the chemical composition of kombucha tea?
Components of kombucha tea include sugars (glucose, fructose and sucrose), organic acids (such as acetic (vinegar), glucuronic, gluconic)), tea polyphenols and ethanol (1,3,9,10). Narrative reviews suggest that kombucha tea contains some nutrients (amino acids, minerals (potassium, magnesium, calcium, iron,), water-soluble vitamins (C, B1, B6, B9, B12), some antibiotic substances and hydrolytic enzymes) (1,3,9,10); quantities varied and the nutritional importance was not discussed. Alcohol content has been found to be as high as 3.5% (2). Most commercial brands contain less than 0.5% ethanol and are considered non-alcoholic (6). The composition of the drink depends on a number of factors including the microbial fermentation mixture, fermentation length, quality of tea, sugar content, temperature and additional ingredients (1).
- Jayabalan R, Malbaša RV, Lončar ES, Vitas JS, Sathishkumar MA. Review on kombucha tea – microbiology, composition, fermentation, beneficial effects, toxicity, and tea fungus. Comprehensive Reviews in Food Science and Food Safety. 2014 July;13(4). Available from: http://onlinelibrary.wiley.com/doi/10.1111/1541-4337.12073/full
- Kombucha Tea. Therapeutic Research Faculty. Natural Medicines Comprehensive Database. [cited 2020 Nov]. Available from: http://naturaldatabase.therapeuticresearch.com. Access only by subscription
- Kapp JM, Sumner W. Kombucha: a systematic review of the empirical evidence of human health benefit. Ann Epidemiol. 2019 Feb;30:66-70. doi: 10.1016/j.annepidem.2018.11.001. Epub 2018 Nov 10. PMID: 30527803. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/30527803/
- Gaggìa F, Baffoni L, Galiano M, Nielsen DS, Jakobsen RR, Castro-Mejía JL, et al. Kombucha Beverage from Green, Black and Rooibos Teas: A Comparative Study Looking at Microbiology, Chemistry and Antioxidant Activity. Nutrients. 2018 Dec 20;11(1):1. doi: 10.3390/nu11010001. PMID: 30577416; PMCID: PMC6356548. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/30577416/
- Villarreal-Soto SA, Beaufort S, Bouajila J, Souchard JP, Taillandier P. Understanding Kombucha Tea Fermentation: A Review. J Food Sci. 2018 Mar;83(3):580-588. doi: 10.1111/1750-3841.14068. PMID: 29508944. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/29508944/
- BC Centre for Disease Control Food Safety Assessment of Kombucha Tea Recipe and Food Safety Plan. Environmental Health Services Food Issue Notes from the field. March 2020. http://www.bccdc.ca/resource-gallery/Documents/Educational%20Materials/EH/FPS/Food/kombucha1.pdf
- Nummer BA. Kombucha brewing under the Food and Drug Administration model Food Code: risk analysis and processing guidance. J Environ Health. 2013 Nov;76(4):8-11. PMID: 24341155. Abstract available from https://pubmed.ncbi.nlm.nih.gov/24341155/
- CFIA. Bacterial Pathogens in Fermented Tea (Kombucha) – April 1, 2018 to March 31, 2019. Available from: https://www.inspection.gc.ca/food-safety-for-industry/chemical-residues-microbiology/food-safety-testing-bulletins/2019-12-23/bacterial-pathogens-in-fermented-tea/eng/1577143157877/1577143158283
- Chakravorty S, Bhattacharya S, Chatzinotas A, Chakraborty W, Bhattacharya D, Gachhui R. Kombucha tea fermentation: Microbial and biochemical dynamics. Int J Food Microbiol. 2016 Mar 2;220:63-72. doi: 10.1016/j.ijfoodmicro.2015.12.015. Epub 2016 Jan 7. PMID: 26796581. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/26796581/
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central. 2019. Available from: fdc.nal.usda.gov