Fermented foods and beverages have been gaining popularity on the grocery shelves. Familiar fermented foods include sauerkraut, kimchi, kefir, dry fermented sausage, yogurt, cheese, kombucha, olives and miso. Surprisingly, Kombucha isn’t new. There have been reports of this fermented tea being consumed in China 2000 years ago! Unfortunately, despite the historical consumption of Kombucha, there have been few human studies designed on the benefits and risks of consumption. The studies that have been performed have been in cell dishes or studied on rats and mice. But before we dive into Kombucha specifically, let’s gain a better understanding of what is known about fermented foods, how they support human health, and the underlying mechanisms that supports these effects. Afterward, we’ll discuss Kombucha precautions and overall health benefits.
What Do Scientists Know About Fermented Foods?
Fermented foods are raw materials (that typically contain a base of sugar/ starch) combined with microorganism(s) that produce certain byproducts with special characteristics of taste and texture.
Under specific conditions such as space and length of time, raw materials can be fermented into high quality foods. Based on the organism used and the source of food, one can create varying degrees of acidity and texture through the fermentation process.
Here are some of the major ingredients and steps in the fermentation process:
How Are Fermented Foods Beneficial?
One of the major benefits of fermented foods is food preservation. The act of fermentation helps to prevent self-contamination. It also comes with the added benefit of unique tastes and textures compared to the original ingredients. Some foods depend on fermentation in order to be edible altogether.
For example, the raw material Saccharomyces cerevisiae (yeast) together with lactic acid bacteria are responsible for the leavening effects of dough. This produces one of the most tasty components of a Western diet:
When it comes to the health benefits of fermented foods, there have been large prospective studies comparing fermented food to weight management and chronic diseases. These are weak in repeatable evidence-based data. While there have been statistically significant associations comparing food types with targeted outcomes, the data does not support a direct cause and effect.
With that being said, there are strong associations between intake of fermented foods and reductions in cardiovascular disease, type 2 diabetes, weight management, and overall mortality.
When we consume fermented food / beverages like kimchi, kefir, kombucha, or miso, we are actually consuming living cells; upwards of 1,000,000 – 1,000,000,000 cells in ONE milliliter! A strong majority of these cells survive along the entire course of our digestive tract.
This is a good thing! This spruces up the bacteria and microbes we already have lining our intestines which is usually significantly reduced in the context of antibiotic use and a highly processed, sanitized Western diet. It also helps to reduce inflammation.
What Are The Underlying Mechanisms That Support These Health Benefits?
When certain microorganisms are paired with raw materials, they become activated. This propels a change in the overall properties and organic chemistry of the original raw materials in a way that can benefit human health.
A great example of this is demonstrated in those who are lactose intolerant. Within dairy products, cheese is generally tolerated better than others by lactose intolerant individuals due to the fermentation process of milk.
For example, when milk is used to create cheese, some of the milk lactose initially gets “eaten up” in the fermentation process. The remaining lactose is separated into whey when the cheese becomes processed. As a result, there is a significant reduction in the amount of lactose being exposed to the gut. Less lactose = less unpleasant GI symptoms! Nice!
Along the lines of improving GI symptoms, sourdough fermentation utilizes a lot of sugar content in the raw starting ingredients (ie: oligosaccharides, disaccharides, monosaccharides, polyols–> FODMAPS). This is partially due to the longer fermentation times. When the content of these elements are well utilized in wheat and rye breads, they promote better tolerance and absorption in the gut.
Less FODMAPS = less unpleasant GI symptoms!
One by-product of the fermentation process is lactic acid. Lactate may quiet inflammatory signals in the body; especially in the intestine. However, this depends on the concentration of lactate. If lactic acid accumulates too heavily in the body, there can be major health consequences that can lead to hospitalization [see cautions of Kombucha below].
Beneficial byproducts include B vitamins (folate, riboflavin and B12) which are produced by certain strains of bacteria in plant and dairy foods during the fermentation process.
Also, the major building blocks for muscles, tissues, organs, hair and skin (amino acids) and nerve signaling chemicals (neurotransmitters) are produced in fermentation.
Kombucha- A Functional Food
A functional food is a whole food with potential health benefits after becoming fortified, enriched, or enhanced. Kombucha tea is created by fermenting sugared black tea with both yeast and bacteria. During the fermentation process of Kombucha, the yeast and fungus create a “tea fungus.” Certain byproducts that are produced (ethanol and acetic acid) protect the tea fungus from becoming contaminated.
Other byproducts include carbonic acid and carbon dioxide which gives the drink it’s fizzy taste. It’s taste is most similar to apple cider; both mildly acidic and alcoholic. The degree of vinegar-like taste is dependent on the length of fermentation time because of the accumulation of organic acids that are produced over time. Short fermentation periods produce a Kombucha tea that is fruity, sour, and lightly carbonated. Longer fermentation times increase the vinegar tasting content of the beverage.
What Are The Safety Concerns / Hazards of Kombucha?
Most adverse effects of Kombucha are related to the acidity of the drink and production of acetic acid, which helps in prevention of contamination. The amount of acid produced is controlled during the fermentation phase. Caution is necessary for individuals who consume Kombucha in high quantities, who have kidney impairment, immune system compromise, and women who are pregnant and lactating.
When making Kombucha home-made, it is very important to ensure proper sanitation of storage containers and appropriate measures to prevent contamination. Talk with your doctor regarding safety of Kombucha consumption. Below are some safety cautions and hazards to be aware of regarding Kombucha.
Despite the inhibitory growth effects of the bacteria and yeast in Kombucha, harmful bacteria are still capable of contaminating batches. Until the pH of the Kombucha batch is fermented down to pH <4.2, there is a potential for mold to grow- especially in home-made batches.
Species such as Aspergillus can have cancer /toxic properties. Therefore, it is extremely important for those who have compromised immune systems to be cautious about drinking potentially contaminated Kombucha.
In addition, there have been a few cases over the years of patients who have had significant adverse events to drinking Kombucha. These case reports included patients with liver damage, metabolic acidosis, allergic reactions, nausea, shortness of breath, throat tightness, headache, dizziness, and jaundice. It it unclear if this is related to a particular batch of Kombucha, how the Kombucha was processed, or how much Kombucha was consumed.
How the Kombucha is stored is also important. There have been severe lead poisoning reports from Kombucha preparation in ceramic pots due to the leaching effects of the acidic acid produced during fermentation. It is paramount that Kombucha is prepared in glass containers to prevent leaching of toxic elements into the tea batch.
During fermentation, several organic acids are produced which have the potential to accumulate and cause liver and kidney damage if levels become high enough. This is especially dangerous in patients who have compromised immune systems and kidney function impairment.
Kombucha is contraindicated in pregnant and lactating women.
What Health Benefits Come With Consuming Kombucha?
Prior to digging deep into the health benefits of Kombucha, it is noteworthy to emphasize that the scientific data in human studies is severely lacking. Most research and data has been conducted on cell studies in Petri dishes and in mice/ rate studies. Please keep this in mind when reviewing the health benefits of Kombucha.
According to a review article of Health, Wellness, and Safety Aspects of the Consumption of Kombucha in the Journal of Chemistry:
Kombucha beverage is known to possess many prophylactic and therapeutic benefits; it is believed to help in digestion, give relief against arthritis, act as a laxative, prevent microbial infections, combat stress and cancer, provide relief against hemorrhoids, impart a positive influence on the cholesterol levels, and facilitate excretion of toxin as well as blood cleansing.”
As described previously, Kombucha acts as a probiotic and helps balance the microbiome in our intestinal tract (this is specifically due to glucuronic acid and butyric acid). Relative to scientific studies focused on fermented milk, there are very few (in vitro and in vivo) studies on Kombucha. Of the scientific studies conducted on Kombucha, the alleged health benefits include:
- Improvement in hair, skin, and nail health
- Reduction in stress and nervous disturbances
- Reduction in insomnia
- Relief of headaches
- Prevention of bladder infections
- Improvement of PMS and menopausal hot flashes
- Improvement in vision
- Stimulation of cellular regeneration
- Relief of bronchitis and asthma
- Increase in metabolism
Kombucha has been found to be protective against a wide range of bacteria and fungi. This is likely attributed to the low pH of the beverage. For those interested, Kombucha has demonstrated inhibition of:
- H pylori (peptic ulcers)
- E. coli (diarrhea)
- Entamoeba, pseudomonas
- Staph aureus/ epidermis
- Salmonella, shigella, yersinia, campylobacter
- (and a few others)
Probiotics are living microorganisms that have health benefits in the human body; usually Lactobacillus of Bifidobacterium.
When we are subjected to extended periods of unhealthy / stress-inducing environments (living in extreme environments, chronic psychoemotional discomfort, and dramatic diet changes), the bacteria that coat the lining of our intestine can change. The protective bugs that normally prevent harmful bacteria from settling into our gut lining and eventually enter into our bloodstream are shed and can disappear. This shift can lead to many health issues such as allergies, autoimmune diseases, multiple sclerosis, and transplant infectious disease.
The bacteria and yeast found in Kombucha act to to normalize and support the growth of healthy bacteria in our GI tract. Probiotics not only balance the gut microbiome, but also boost the immune system, aid in improving digestion, prevent overgrowth of harmful bacteria, and stave off anxiety and depression by improving mental clarity and mood.
Population studies have been conducted extensively at The Central Oncological Research Unit in Russia and the Russian Academy of Sciences in Moscow. Effective anticancer agents have been identified in dietary phytochemicals and tea polyphenols. Given the presence of these bioactive compounds in Kombucha, the extrapolation is that daily consumption of Kombucha may have anticancer effects as well.
Tea polyphenols have been shown to; “inhibit gene mutations, inhibit the proliferation of cancer cells, and induce cancer cell [death] and the ability to [stop the spread of cancer cells in the body].
In cancer patients specifically, Kombucha aids in restoration of neutral blood pH. There has also been findings in reduction in stomach cancer incidence attributed to many compounds that are found in Kombucha (ie: polyphenols, gluconic acid, glucoronic acid, lactic acid, and vitamin C). Polyphenols posses anti-tumor properties, thereby acting as a cancer-blocking agent.
In the human body, the liver acts as the main waste receptacle. Kombucha has been found to help the liver detoxify harmful toxins in the body.
During the fermentation process, glucuronic acid is produced when glucose (sugar) is oxidized. This key byproduct binds to toxic molecules in the body. They transport them to the liver, kidneys, and intestines to be discarded. This process is called glucuronidation.
In addition, Kombucha tea has been known to help get rid of harmful environmental pollutants in the human body and to excrete heavy metal substances.
An antioxidant is any substance that delays, or stops, the oxidation of a substrate. (Anyone starting to get PTSD from chemistry class?). During oxidation reactions, free radicals are produced which can start a cascade of harmful chain reactions that ultimately can lead to cell damage or death in the human body. The stress induced by these reactants and reactions are prevalent in Parkinson’s disease, coronary heart disease, and cancer which have been linked to smoking, air pollution, and poor nutrition and exercise.
Antioxidants work to remove these free radicals and prevent the “domino-effect” of chain reactions in the body. Polyphenols found in tea (and Kombucha) work as antioxidants to fight free radicals and reactive oxygen species (aka- prevent the harmful chain reaction as stated above).
What is interesting, is that the level of phenols significantly increases in the fermentation process of Kombucha. Higher levels = higher levels of protection. However, there is a limitation to this. Prolonged fermentation can be harmful due to the accumulation of organic acids that are produced.
Many cell line / animal studies have linked Kombucha with “heptaoprotective activity”; meaning, liver protection from damaging toxins in the body from environmental pollutants. Sparing the details of the process, an overly simplified summary is that Kombucha tea helps in preventing liver cells from dying when exposed to certain environmental toxins. Most of the data comes from studies on rats.
In otherwise healthy individuals- when consumed in moderation- Kombucha has been found to have health benefits. There is still a need for extensive scientific research on human studies to validate these health claims. As always, please be to sure to discuss with your medical provider prior to consumption of Kombucha as appropriate.
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- Jessica Martínez Leal, Lucía Valenzuela Suárez, Rasu Jayabalan, Joselina Huerta Oros & Anayansi Escalante-Aburto (2018) A review on health benefits of kombucha nutritional compounds and metabolites, CyTA – Journal of Food, 16:1, 390-399, DOI: 10.1080/19476337.2017.1410499
- Marco, M L, and E J Smid. “Editorial Overview: Food Biotechnology: Exploration and Exploitation of Microbial Resources to Address the Need for Sustainable Production of Safe, Healthy and Nutritious Food.” Advances in Pediatrics., U.S. National Library of Medicine, 5 Dec. 2017, www.ncbi.nlm.nih.gov/pubmed/29221900.
- Marco, M L, et al. “Health Benefits of Fermented Foods: Microbiota and beyond.” Advances in Pediatrics., U.S. National Library of Medicine, 18 Dec. 2016, www.ncbi.nlm.nih.gov/pubmed/27998788.
- Watawana, Mindani I, et al. “Health, Wellness, and Safety Aspects of the Consumption of Kombucha.” International Scholarly Research Notices, Hindawi, 30 Dec. 2015, www.hindawi.com/journals/jchem/2015/591869/.