After our blog post on kombucha, we received several questions regarding the nature of kombucha’s toxicity, and the risk that comes with drinking it.

To bring you up to speed: kombucha is a fermented drink product, made by fermenting already-fermented green or black tea. This is why kombucha is called ‘doubly-fermented’ tea. However, if kombucha is fermented for too long or in unsanitary conditions, it can develop very dangerous properties.

One of the molecules found in kombucha is called D-saccharic acid 1,4 lactone (D-saccharolactone). D-saccharolactone has been studied for its ability to prevent colon cancer, diabetes and hyperglycemia.

Unfortunately, more research is needed to determine if D-saccharolactone is an effective protective compound when supplemented or consumed through products like kombucha. D-saccharolactone has been shown to be effective when studied in vitro, meaning outside of the body, in a test tube or petri dish, but more studies are needed to determine if these effects extend to oral consumption of kombucha. It is not uncommon for a compound to be very promising in vitro but not do much when consumed (for example, see glutamine).

What sets kombucha apart from other potentially dangerous food products is how little is known about the strains of toxic bacteria and fungi that make improperly brewed kombucha dangerous.

Dangerous food products can fall into several groups:

Spirulina, an algae sometimes used as a supplement, can be dangerous if it is contaminated with microcystin, a kind of toxin. Spirulina producers are aware of this potential danger, and test spirulina for microcystin.

Some herbal supplements can be toxic if they are contaminated with other species of herbs. Herbal producers run tests to make sure their herbal supplements are pure, and subsequently, safe. For example, Stephania tetrandra is one of the four plants that can make up the traditional Chinese medicine Fang Ji. In the past, it has been contaminated with a toxic plant called Aristolochia fangchi, which can also be called Fang Ji. Anyone that produces Stepania supplements knows to test for Aristolochia.

Other food products, when prepared improperly, become toxic or dangerous. Chicken, for example, can be dangerous if it is eaten raw or undercooked. But while you can use a thermometer to determine how safe chicken is to eat, there is no easy test for determining kombucha’s safety. Unlike spirulina, researchers don’t know what fungi and/or bacteria strains are dangerous in kombucha, and which provide the health effects.

Though kombucha may have potential health benefits, it can be dangerous to drink because many of its risks are still unknown. Unsanitary kombucha can cause death, organ failure, and there’s even been one report of cutaneous anthrax. Additionally there has been a new report of a woman who drank kombucha, which was found to not be unsanitary but potentially contaminated, who suffered from liver inflammation.

Any compound that provides unique benefits, but has also been shown to be toxic, can still be supplemented if the toxicity is carefully controlled for. Unfortunately, the specific toxins in kombucha have yet to be identified. More importantly, more research is needed to determine whether kombucha really does provide unique health benefits. With little proven health benefits, and questionable toxicity, Kombucha cannot be recommended for supplementation or consumption at this time. Future evidence must identify the toxic strains in kombucha, or confirm the unique therapeutic effect of saccharolactone (when consumed through kombucha), for kombucha to be recommended as a health drink.

If you do choose to drink kombucha, it is very important to research the producer. Only purchase kombucha from sanitary producers with properly trained staff. Kombucha is not recommended as a therapeutic or preventative drink. Instead, consider options like black or green tea, or fermented food products like kimchi or sauerkraut.