Kombucha vs Kvass
By Shirley Webber (Research Dietitian)
Despite the increasing popularity and the raving magazine articles exclaiming the benefits of fermented drinks such as kombucha and Kvass, few research studies have investigated the effects of these drinks on long term health.
To prepare for this blog, I did an internet search for articles on these drinks and I was overwhelmed with information on the perceived health benefits of drinking fermented drinks and how to prepare them. Some were written with such passion that I almost wanted to reach for the tea bags and fire up my own brew. But as I read these articles, I couldn’t help but notice that none referenced scientific studies. The claims made it sound like there was a lot of hard scientific evidence to support the benefits of these drinks, yet there is still so little that we actually know about the effects of fermented drinks on the body. So what do we know about our newly tested fermented drinks, Kombucha and Kvass?
Kombucha is a fermented drink that has been used in China for centuries. Its use later spread to Europe, particularly Russia and Germany and has now reached worldwide popularity (1,2).
Kombucha is made from tea, sugar and a SCOBY (short for Symbiotic Culture of Bacteria and Yeast). A SCOBY is usually bought online or gifted by another kombucha brewer. The process of making kombucha involves boiling the tea and adding a lot of sugar, then once cooled, adding the SCOBY and letting it sit in a warm, dark place for 5-30 days. The SCOBY ferments (feeds on) the sugar, therefore reducing the sugar content of the drink. The fermentation process increases the tartness of the drink.
What’s the benefit?
Kombucha has long been credited with improving health, however these claims are based on personal observations and testimonials, not scientific evidence (3). Purported health benefits include decreasing blood pressure, increasing vitality, fighting acne, relieving arthritis, eliminating wrinkles (that’s enough to get us all drinking it – am I right?) and alleviating constipation(4). The list goes on! These observations may be attributed to the antioxidant and probiotic content of the drinks (2).
Despite the reported benefits of Kombucha, the drink (especially if home brewed) may also cause some undesirable effects, with side effects such as dizziness, nausea, vomiting, headaches, neck pain, shaking, shortness of breath, tightening of the throat, hypotension, and allergic reaction all previously reported (2,4). Therefore, it is extremely important that you know the conditions in which your kombucha has been prepared and be aware of the risks of consuming a home brewed kombucha. If accepting a SCOBY from a friend, make sure the SCOBY is sourced from a safe and hygienic environment.
What bacteria does Kombucha contain?
Kombucha has been found to contain 5 bacterial phyla: Actinobacteria, Bacteroidetes, Deinococcus-Thermus, Firmicutes and the dominant bacteria, Proteobacteria (with the main genus being Gluconacetobacter and to a lesser extent Acetobacter) (2).
Kvass is a cereal based fermented drink predominantly used as a soft drink. It is made by fermenting cereals such as rye and barley malt, rye flour and stale rye bread. Another version of Kvass is made from water, rye bread, sugar, yeast, juniper berries and raisins. There is also a mint variety where mint may be added during processing (2). The process of making kvass involves baking the boiling the rye bread and uses a sourdough culture to keep the fermentation process going.
What’s the benefits?
Despite bold claims about the health benefits of drinking Kvass, there is little scientific evidence to support these. Claims include that the drink enhances immune function, prevents infection, relieves diarrhoea, protects against chronic health conditions and assists in managing inflammatory bowel disease and irritable bowel syndrome . Although these claims are not supported by scientific evidence, interest in this drink is brewing.
What bacteria does kvass contain?
Kvass is rich in microbiota from LAB (Lb. casei, Ln. mesenteroides) and yeasts (Saccharomyces cerevisiae), however the levels in which they are found can vary depending on the method of fermentation used (2).
FODMAPs in fermented drinks
Kombucha (plant based) has been found to contain fructans. Therefore, a full serving of this drink may not be suitable for those who do not tolerate fructans. Please see the Monash app for serving size suggestions.
Kvass (cereal based) is low in FODMAPs in a single serve. Again, please see the Monash app for safe serving sizes.
Please note that we did not test home brewed drinks, rather a number of different commercially available products.
As kombucha and kvass are fermented drinks, they may contain a small percentage of alcohol. Therefore, these drinks should not be consumed by children, pregnant women, those who have alcohol sensitivities or alcoholics wanting to abstain from alcohol. If you experience any adverse effects from kombucha or kvass, please seek the advice of your doctor.
There is yet to be a clinical research trial to directly link fermented drinks to health benefits. This is not to say they are not healthy to consume, just that we don’t yet know their effects! Because there are some risks associated with drinking home brews, caution needs to be given to drinking home brewed fermented drinks.
1. Ernst E. Kombucha: A systematic review of the clinical evidence. Forsch Komplementärmed Klass Naturheilkd. 2003;10:85-87.
2. Baschali A, Tsakalidou E, Kyriacou A, Karavasiloglou N, Matalas AL. Tranditional low-alcoholic and non-alcoholic fermented beverages consumed in European coutries: a neglected food group. Nutr Res Rev. 2017: 1-24.
3. Vina I, Semjonovs P, Linde R, Denina I. Current evidence on physiological avtivity and expected health effects of kombucha fermented beverage. J Med Food. 2013 Sep 2;17(2):179-188.
4. Srinivasan R, Smolinske S, Greenbaum D. Probable gastrointestinal toxicity of Kombucha Tea. J Gen Intern Med 1997; 12:643-644.