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Fermented Foods and Cancer

Fermented Foods and Cancer

2015 - 10 - 19

Sauerkraut Bread, yogurt, sauerkraut, cheese, vinegar, and beer. What do all of these foods have in common? All of the above (and many other foods) are fermented. Fermented foods have recently gained a lot of positive attention, and for good reason. Fermented foods are filled with concentrated nutrients, probiotics, and good bacteria, many of which we use routinely in our one hundred trillion bacteria strong gut microbiota.1  

[Editor’s note: This is not to say that we recommend all of the above foods].

The Mutual Relationship

Microbes present in the gastrointestinal (GI) tract have the potential to behave in a favorable, a harmful, or a neutral manner.2 Overall, there is a mutual relationship between humans and gut flora, with a goal of achieving a balance between good and bad bacteria. Although not essential for survival, our gut flora is considered a “forgotten organ”3 that aids in several different bodily processes. For example, gut flora improves immune function, increase absorption of water, control metabolic function, and fight pathogenic bacteria that could cause harm to us.4 Unfortunately, poor diet, broad-spectrum antibiotic use, and inflammation can cause our gut flora to get out of balance or to be wiped out completely.5,6 The good news is that we can realign our gut flora by consuming fermented foods.

Around the turn of the last century, microbiologists noticed that gut flora in healthy individuals bear little resemblance to those of sick individuals.2 The beneficial microflora in the GI tract were termed probiotics, literally meaning “for life.”7 Over the past hundred years or so, scientists have learned that we can treat several chronic diseases, including irritable bowel syndrome, Chron’s disease, and cancer with probiotics.2 Gene expression is particularly influenced by gut microflora: Research has shown that probiotics influence several genes, aiding them to express in a beneficial, disease-fighting manner.8

Probiotics Versus Cancer

Cancer is a complicated disease with different phenotypes and origins. One of the ways cancer develops is through exposure to carcinogens, some of which can be ingested or generated by an abundance of harmful gut flora like e-coli.9 Probiotics may decrease the body’s exposure to ingested carcinogens by several different processes, including aiding with detoxification, improving apoptosis (programmed death of damaged cells), inhibiting tumor growth, and stimulation of the immune system.2,10


Probiotics help detoxify the body through several different mechanisms, often dependent upon the probiotic strain. Bifidobacterium breve and Lactobacillus casei, found in foods like sauerkraut and kefir (see Fermented Foods below for more information), both reduce intestinal absorption by facilitating the excretion of toxicants such as Bisphenol A (BPA).11 Bifidobacterium breve in particular has shown to improve the intestinal environment of immunocompromised patients undergoing chemotherapy.12 Furthermore, Lactobacillus strains of bacteria help prevent heavy metal toxicity through binding and excretion of harmful heavy metals as well as reduce toxicity of mutagenic heterocyclic aromatic amines (HCA), found in overcooked meat.13,14 Kimchi, a fermented cabbage dish, contains probiotic strains that degrade organophosphorus pesticides by using the toxins as food, and breaks down sodium nitrate, a cancer-causing food preservative.15,16 These are just a few examples of detoxification methods by probiotics.

Apoptosis and tumor death

Apoptosis is the process of programmed cell death. It is a highly regulated and controlled process that 50-70 billion cells undergo every day in a human adult.17 This process is essential when there is a cell that no longer functions correctly or has DNA damage. The last thing you want is a damaged cell reproducing to form more damaged and malfunctioning cells. A failure in the apoptosis pathway can result in the proliferation of malfunctioning cells, which can turn into malignant tumors.18 Some strains of probiotics can regulate apoptosis in a variety of ways. Probiotics are exceptionally effective in suppressing colon cancer growth, and emerging studies show promise that probiotics can be used to inhibit the incidence of liver, small intestinal, and breast cancer.19,20 For example, the Propionibacterium freudenreichii strain, found in Swiss-type cheeses, kills cancerous colon cells through a shift in the cells’ extracellular pH.

Fermented Foods

One of the best ways of boosting beneficial gut flora is by ingesting probiotics through fermented foods. Fermentation is a natural metabolic process that converts carbohydrates into acid or alcohol and gas. Under anaerobic (oxygen starved) conditions, the fermentation of foods occurs using yeast, bacteria, or a combination of the two.25 One of the most well studied fermentation processes is lactic acid fermentation, whereby lactic acid bacteria anaerobically convert sugar into lactic acid, a preservative.26 It is ideal to consume a variety of fermented foods, as each one will introduce and inoculate the gut with different probiotics.18 These include:

  • Fermented vegetables (cabbage, carrots, kale, cucumbers): Sauerkraut is probably the most well-known fermented vegetable, and high-quality ones are sold in the refrigerated section of many stores. Check the ingredient list, however, because those made with vinegar are pickled and not fermented.
  • Fermented raw milk (kefir and yogurt): Commercial yogurts may not have live cultures and are oftentimes loaded with sugar, so check the label before purchasing.
  • Tempeh: Fermented soybeans that are frequently used as a meat substitute.
  • Kombucha: a drink made from sweetened tea fermented with a symbiotic culture of bacteria and yeast called a “mother.”
  • Miso: soybean, rice, or barley paste fermented with koji mold, and usually used in soups and dressings.
High-quality probiotic supplements are also available for those who don’t like or don’t have access to fermented foods, and generally work well. Keep in mind that probiotics are sensitive to oxygen, temperature, and moisture.27 It is always advisable to try to ingest probiotics via a variety of organic fermented foods, as commercially produced products containing probiotic bacteria are often overhyped, mislabeled, and potentially contaminated.28

A great cost-effective way of having fermented foods is to make them yourself, the basics of which consist of vegetables you want to ferment, salt, and a fermentation jar.29 A fantastic, good-for-your-gut recipe for a beginner to make is sauerkraut:30

Caraway Sauerkraut

(Adapted from Nourishing Traditions, by Sally Fallon) Makes 1 quart

  • 1 medium head of cabbage, cored and shredded
  • 1 tbs. caraway seeds (optional)
  • 2 tbs. sea salt
  • 1 quart-sized, wide-mouth canning jar with lid
In a large bowl, mix all the ingredients together. Press with the rounded bottom of a ladle to release the juices. Transfer the cabbage into the canning jar and press down firmly until the juices cover the cabbage. The top of the cabbage should be at least 1 inch below the top of the jar. Cover tightly and keep at room temperature for about three days before transferring to the refrigerator. The sauerkraut may be eaten immediately, but it tastes best if you store it in the refrigerator for at least a week.


If you are new to probiotics and are attempting a shift in your diet, consume a small amount of fermented foods and gradually eat more as your gut flora adjusts; this helps avoid any gas or bloating.29


Our bodies are constantly trying to achieve a state of equilibrium in gut flora. Modern lifestyles, with commercially processed foods and broad-spectrum antibiotics, shift this balance over to the pathogenic, or bad, gut bacteria. The end result is poor gut health, sickness, and obesity. We can reseed the gut by consuming fermented foods teeming with probiotics, and allow the body to realign and rebalance itself for optimum health.

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[10] Aso, Y. and Akazan, H. (1992) Prophylactic effect of a Lactobacillus casei preparation on the recurrence of superficial bladder cancer. Urology International. 49(1): pp. 125-129.

[11] Oishi, K., Sato, T., Yokoi, W., Yoshida, Y., Ito, M., and Sawada, H. (2008) Effect of probiotics, Bifidobacterium breve and Lactobacillus casei, on Bisphenol A exposure in rats. Bioscience, Biotechnology, and Biochemistry. 72(6): pp. 1409-1415.

[12] Wada, M., Nagata, S., Saito, M., Shimizu, T., Yamashiro, Y., Matsuki, T., Asahara, T., and Nomoto, K. (2010) Effects of the enteral administration of Bifidobacterium breve on patients undergoing chemotherapy for pediatric malignancies. Support Care Cancer. 18(6): pp. 751-759.

[13] Monachese, M., Burton, J., and Reid, G. (2012) Bioremediation and tolerance of humans to heavy metals through microbial processes: A potential role for probiotics? Applied Environmental Microbiology. 78(18): pp. 6397-6404.

[14] Nowak, A. and Libudzisz, Z. (2009) Ability of probiotic Lactobacillus Casei DN 114001 to bind or/and metabolise heterocyclic aromatic amines in vitro. European Journal of Nutrition. 48(7): pp. 419-427.

[15] Cho, K., Math, R., Islam, S., Lim, W., Hong, S., Kim, J., Yun, M., Cho, J., and Yun, H. (2009) Biodegradation of chlorpyrifos by lactic acid bacteria during kimchi fermentation. Journal of Agricultural Food Chemistry. 57(5): pp. 1882-1889.

[16] Oh, C., Oh, M., and Kim, S. (2004) The depletion of sodium nitrite by lactic acid bacteria isolated from kimchi. Journal of Medicinal Food. 7(1): pp. 38-44.

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[20] Kumar, M., Kumar, A., Nagpal, R., Mohania, D., Behare, P., Verma, V. et al. (2010) Cancer-preventing attributes of probiotics: An update. International Journal of Food Science and Nutrition. 61(5): pp. 473-496.

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[29] Paleo Leap (2015) Fermented Food Recipes [online]. Available at: [Accessed 11 September 2015].

[30] Olson, K. (2014) Discover Fermented Foods [online]. Available at: [Accessed 6 October 2015].

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