Kombucha is a probiotic beverage that is believed to have benefits for the gut, heart, and blood sugar. Does it work, and how is it made? Read on to learn more.
What is Kombucha?
Kombucha is a beverage made from tea, sugar, yeast, and bacteria. A culture of acetic bacteria and fungi (Symbiotic Colony of Bacteria and Yeast, or SCOBY) ferments the sugared tea. Originally from China, the beverage made its way to Korea, Japan, and Russia, where its health benefits became well known [1].
Traditionally, Kombucha is made using white sugar and black tea, but can also be made with green or oolong tea. After the tea is prepared, sugar, starter culture, and tea fungus are added to the mixture to ferment the tea for one to eight weeks [1].
After this fermentation period, kombucha is ready to be taken out and stored in a clean container. It is consumed after fermentation is finished [1].
Kombucha is believed to have many health benefits for immune function, inflammation, heart disease, and digestion [1].
Antioxidant Activity
The antioxidant activity in tea and Kombucha can be attributed to their catechin and polyphenol content from the tea leaves [1].
The fermentation process increases free radical scavenging activities in Kombucha, so Kombucha has even higher antioxidant activity than unfermented tea [2].
Health Benefits of Kombucha
Although kombucha has many health benefits, its safety is not guaranteed because most of the studies are done on rats and other animals. More human studies must be done before its health benefits can be confirmed.
Kombucha is considered safe to drink for most people, but it has not been approved by the FDA for any health purpose and generally lacks solid clinical research.
Insufficient Evidence For
The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of kombucha for any of the below-listed uses. Kombucha is considered safe for most people, but it should never be used in place of something your doctor recommends or prescribes.
1) Gut Health
Kombucha is a probiotic drink. Some researchers believe that the microorganisms found in the tea may balance intestinal microbiota, improve digestion, fight against harmful bacteria, and aid gut processes [3].
The bacteria and yeast used in the fermentation process have been found to promote the growth of beneficial microbes in the intestine. When humans are exposed to unhealthy environments, their gut microbiota can change and harm their health. The microbes in kombucha have been found to revert some such changes and keep the human gut healthy [3].
Animal & Cell Research (Lacking Evidence)
No clinical evidence supports the use of kombucha for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
2) Blood Sugar
Both green and black tea extracts significantly lowered blood glucose in rats [1].
In diabetic rats, kombucha was a better suppressor of high blood glucose levels than black tea. Kombucha polyphenols prevented the damage and death of pancreatic β-cells, which play a role in insulin secretion [4].
Additionally, some researchers have suggested that kombucha’s antioxidant properties may also help protect against diabetes-related complications [3].
3) Heart Health
In rats, tea extracts reduced total cholesterol and inflammation. It also reduced blood pressure and prevented obesity. All of these effects can help lower the risk of developing heart disease [1].
4) Detoxification
Kombucha’s antioxidant activity may also help during detoxification in the liver [2].
Glucuronic acid most likely contributes to most of kombucha’s detoxifying properties. Glucuronic acid binds to toxin molecules to increase their excretion from the body. It expels drugs, pollutants, steroids, and bile acids out of the body [1].
Additionally, kombucha contains measurable amounts of glucaric acid. Glucaric acid increases the efficiency of the liver’s detoxification pathways. It does this by eliminating waste the first time instead of letting it become reabsorbed and detoxified repeatedly [4, 5].
Malic acid, another product of tea fermentation, is similar to glucuronic acid. It is also believed to help in detoxification in the liver by binding with toxic metals and eliminating toxins [3].
Kombucha’s toxin removal action may help patients obtain relief from gout, arthritis, and kidney stones. However, there are no human studies yet [3].
5) Antimicrobial Activity
Kombucha tea can inhibit many pathogenic microorganisms. Black tea and green tea Kombucha possesses greater inhibitory activity compared to oolong [2].
Kombucha can inhibit the growth of bacteria and various fungi [3].
The presence of organic acids, particularly acetic acid, large proteins, and catechins in the beverage contributes to its antimicrobial activities [2].
- Kombucha has in vitro antimicrobial efficacy against Agrobacterium tumefaciens, Bacillus cereus, Salmonella choleraesuis serotype Typhimurium, Staphylococcus aureus, and Escherichia coli [2].
- It also inhibits the growth of Entamoeba cloacae, Pseudomonas aeruginosa, B. cereus, E. coli, Aeromonas hydrophila, Salmonella typhimurium, Salmonella enteritidis, Shigella sonnei, Staphylococcus epidermis, Leuconostoc monocytogenes, Yersinia enterocolitica, Campylobacter jejuni, Helicobacter pylori, and Candida albicans [2].
Cancer Research
Kombucha’s antioxidant activity is believed to have potentially anticancer consequences [3], but there are no clinical trials done on the subject.
EGCG, a major tea polyphenol, can stop cancer cell growth in a dish [1].
In a cell-based study, Kombucha tea extract decreased the survival of prostate cancer cells and prevented blood vessel formation [2]. It does this by inhibiting inflammatory genes such as COX2, IL-8, HIF-1alpha, MMPs, VEGF, and other growth-promoting genes inside of the cancer cells.
Also, the polyphenols, gluconic acid, glucuronic acid, lactic acid, and vitamin C present in Kombucha have been shown to reduce the occurrence of stomach cancer [3].
There are no clinical trials done on Kombucha and cancer, so it’s unknown if it has any anti-cancer effects in humans. Studies on isolated cancer cells very rarely translate to activity in animals or humans.
Healthy Components of Kombucha
Kombucha is rich in a number of bioactive and potentially beneficial compounds. These have been extensively studied on their own, outside of the context of kombucha. It is unclear to what extent these studies apply to kombucha as a whole, but researchers may use these studies as a jumping-off point for future research into this probiotic beverage.
1) Tea Polyphenols and Amino Acids
Many health benefits of Kombucha intake are similar to those of regular tea consumption, including the immune stimulation, digestive improvement, and improved metabolism [1].
This is because most of the polyphenols and amino acids found in green and black tea are still present in Kombucha after fermentation [1].
Tea contains chemicals called catechins and polyphenols. They contain many health benefits, which is partly why tea extracts are increasingly used in dietary and health supplements [6].
Some of the most important beneficial substances in tea include EGCG, theanine, and caffeine.
2) Glucuronic Acid
Glucuronic acid may contribute to most of Kombucha’s detoxifying properties. Glucuronic acid binds to toxin molecules to increase their excretion from the body. This process is known as glucuronidation [1].
Glucuronidation is involved with the expulsion of drugs, pollutants, steroids, and bile acids. Hormones can also be glucuronidated for easier transport throughout the body [7].
Glucuronic acid works with butyric acid, also found in Kombucha, to strengthen the gut walls and protect against parasites [3].
In rats, the glucuronic acid from Kombucha ameliorated pollutant-induced kidney damage. It helped repair the liver and protect against damage by metabolizing toxins [8].
However, Kombucha actually doesn’t have that much glucuronic acid. Its detoxifying properties might come from other acids found in the beverage [1].
3) Gluconic Acid
One of the main products of the fermentation process is gluconic acid. The acetic acid-producing bacteria converts glucose to gluconic acid by breaking down caprylic acid. This process helps prevent certain types of yeast-based infections [3].
Gluconic and butyric acid work together to strengthen the gut walls during yeast infections, thus protecting the digestive system [3].
4) Glucaric Acid (Glucarate)
Additionally, kombucha contains measurable amounts of glucaric acid. Glucaric acid increases the efficiency of the liver’s detoxification pathways. It does this by blocking the enzyme beta-glucuronidase. This increases the excretion of toxins and toxin reabsorption repeatedly in the liver and the gut [4, 5].
There is ongoing research into the use of glucaric acid to prevent breast, colon, and prostate cancer [9].
5) Acetic Acid
In kombucha, acetic acid bacteria convert fructose (sugar) into acetic acid. The acetic acid can prevent fungal growth. It can also work with other kombucha constituents to stop microbes [1].
In rats, acetic acid can help lower total cholesterol levels. Rats fed vinegar also have lower blood pressure than animals fed a diet not enriched with vinegar. These effects are associated with lower rates of heart disease [10].
Vinegar’s main component is acetic acid. When patients took vinegar with food, their feeling of fullness increased. This reduced the amount of food consumed. Daily intake of 750 mg acetic acid might help reduce obesity [11].
- Kombucha contains the following acetic bacteria: Acetobacter xylinum, A. xylinoides, Bacterium gluconicum, A. aceti, and A. pasteurianus [1].
6) Butyric Acid
The Kombucha fermentation process forms butyric acid. It protects human cell membranes [3].
Butyric acid works with glucuronic acid to strengthen the gut walls and protect against parasites. It also has the ability to enhance blood circulation and prevent constipation [3].
Also, it inhibits tumor cells in the colon while simultaneously promoting healthy colon cells.
Butyric acid is an HDAC inhibitor that suppresses the IFN-γ/STAT1 signaling pathways and eliminates the source of inflammation [12].
7) Lactic Acid
Lactic acid is one of the main metabolites of kombucha. There is a higher concentration of lactic acid in green tea kombucha than in black tea preparations [1, 2].
When lactate is available in the brain, it supplements glucose and supports an increase in energy metabolism [13].
In humans, neurons in the brain use lactate for energy. Glial cells transform glucose into lactate and provide lactate to neurons. Lactate also plays an important role in the early stages of brain development [13].
8) Malic Acid
Malic acid, another product of tea fermentation, is similar to glucuronic acid. It helps with detoxification by binding with toxic metals and eliminating toxins [3].
Malic acid is often used as a supplement that helps with mitochondrial health. It helps reduce muscle fatigue while aiding muscle performance and preventing pain [14].
Malic acid can also improve skin condition. It tightens skin pores, which increases smoothness and reduces the appearance of wrinkles. While it is safe to use, topical malic acid does have side effects. Skincare products with malic acid in them may cause rashes, hives, or the sensation of tightening in the chest [15, 16].
9) Usnic Acid
Older studies have reported the presence of usnic acid in kombucha, but recent studies have not confirmed its presence. Usnic acid deactivates some groups of viruses on direct exposure [1].
Usnic acid is a potent antibiotic that is effective against bacteria and fungi. It also has anti-inflammatory properties [17].
In the United States, some food supplements for weight reduction use usnic acid. However, there is no proof for these claims. Daily oral intake of these supplements may cause severe liver damage [18].
10) Oxalic Acid
Oxalic acid is a byproduct of the kombucha fermentation process [3].
It can be useful during the production of ATP, which plays a vital role in energy metabolism [3].
Oxalic acid’s conjugate base inhibits the lactate dehydrogenase (LDH) enzyme. LDH inhibition prevents anaerobic energy metabolism. Because cancer cells prefer to use anaerobic metabolism, this inhibition can stop tumor formation and growth of cancer cells [19, 20].
11) Probiotics
The bacteria and yeast in kombucha are probiotic species [3].
These microorganisms help boost the immune system, balance intestinal microbiota, improve digestion, and fight against harmful bacteria growth [3].
When humans are exposed to unhealthy environments, their gut microbiota can change and harm their health. Kombucha can help revert the changes and keep their gut healthy [3].
12) Ethanol
The acetic acid in kombucha stimulates yeast to produce ethanol. In turn, ethanol helps acetic acid bacteria grow and produce acetic acid [1, 21]. Most kombucha on the market has only a small amount of ethanol (around 0.5%).
Ethanol has antimicrobial properties against harmful bacteria. It can also help prevent contamination of the tea fungus [21].
13) Sugar
During the fermentation process, yeast breaks down sucrose (sugar) into fructose and glucose [1].
A perfect ratio of sucrose and tea is needed to make the optimal concentration of ethanol and lactic acid. Sucrose is the main source of carbon during the fermentation process [2].
The kombucha fermentation process can use other types of sugar, such as molasses, to provide carbon, but it makes a lesser quality product. Sucrose is mandatory for a high yield and quality [22].
14) B Vitamins
In one study, a kombucha beverage made from sucrose and black tea was found to contain vitamin B1, vitamin B2, vitamin B6, and vitamin B12 [2].
Some believe that the Vitamin B complex content in kombucha may aid nervous system function simply because the B vitamins are vital to such functions, but there is not enough direct evidence to support this claim [1].
15) Other
The fermentation process for kombucha may produce hyaluronic acid and chondroitin sulfate acid. However, there is not enough evidence for this [23].
Side Effects and Caution
While Kombucha may show many health benefits in animal studies, there is not enough evidence that these effects will be present in humans. There are many case studies and reports of adverse reactions to this beverage [24].
Some people experience allergic reactions and upset stomachs after drinking Kombucha beverage [1].
Excess levels of certain acids from the beverage can cause liver and kidney toxicity [3].
Additionally, people with compromised immune systems should refrain from drinking the beverage because it contains live microorganisms, which can cause infections [3].
People have also died after drinking large amounts of potentially contaminated Kombucha [25], although the exact cause of the death was unclear.
If you make your own Kombucha at home, contamination is possible. You should properly store Kombucha in order to prevent food poisoning and toxic reactions [1].
People with histamine intolerance or mast cell activation disorder may react negatively to kombucha, because it is a fermented food.
