What Are Fermented Foods?

What Are Fermented Foods?

Kara Jacobson

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If you’re reading this, you’ve probably heard about fermented foods, and maybe even tried a few. Given the growing evidence to support ingesting them, we thought it would be helpful to break down what they are and what they do. Let’s do it!

Fermented foods are foods or drinks made by utilizing microbes to convert compounds in food into other things over time.1 That process is called fermentation. Just like wine relies on fermentation to convert the compounds in grapes to a well-balanced glass of the good stuff, kombucha relies on fermentation to convert the compounds in tea to a delicious fizzy probiotic beverage. Fermented foods have been enjoyed for thousands of years across countless cultures for preservation, enjoyment, and health!1 And in the last two decades we’ve seen a resurgence in fermented food popularity, particularly in the US. Today, the four most popular fermented foods in the US (apart from alcoholic drinks) are kefir, kombucha, probiotic yogurt and sauerkraut.1 Let’s start with those!

Simply put, there are endless ways to ferment! The reason is that there are so many bases to work from, so many microbes available to introduce, and so many variables you can play with in the process. For example, one batch of sauerkraut may be different than the next EVEN if you’re using the same exact recipe. Simply because the head of cabbage is a wee bit different than the one you used last time. For this reason, there really is no ONE way to ferment.
Loosely though, the process looks something like this:

  1. Mix a) base food, b) usually, but not always, some sort of sugar, and c) microbes into fermentation vessel. Microbes can be manually added or naturally occurring within base food.
  2. Have mix sit over time, usually weeks, for fermentation to occur. The “sitting” can be without air (or anaerobic), with air (aerobic), or a combo!
  3. Get a fork or straw and enjoy!

Well for one, they’re delicious. Fermentation truly transforms food! It creates all kinds of tasty byproducts (also called metabolites) in the process. Fermentation adds things like complexity, acidity, robustness, bubbles, and all kinds of aromatics and flavor profiles to the original food. As they say, a great wine is NOTHING like grape juice — and we have fermentation to thank.

Besides just the taste, fermented foods are generally really good for you.1-4 There are 2 reasons for this:

  1. The microbes used in fermentation replicate, and often remain in the ending food or drink you ingest, acting as probiotics (which we know are good for your gut).2,3
  2. The metabolites produced in fermentation often can’t be sourced easily anywhere else AND have a very important health benefit.2,4



So what exactly are the health benefits of eating fermented foods? There are hundreds of studies* on how they impact health. To help simplify, I’ve narrowed it down to the four most widely studied and accepted health benefits.

  1. Fermented foods are likely ANTI-MICROBIAL against “bad” pathogens. Numerous studies show that fermented foods resist the growth of things like Salmonella, H.Pylori (that’s the bacteria that causes most ulcers), and E.Coli!6,8,13,15. Our ancestors already knew this, which is why they used the process of fermentation for hundreds of years to preserve food from rotting (by keeping it safe from the “bad” bacteria and yeasts that break it down).

  2. Fermented foods are likely ANTI-INFLAMMATORY. While these are mostly studies done on animals, it should be noted there are numerous trials on fermented foods (specifically those with lactic and acetic acid) that show that when consumed both topically and orally, these compounds result in accelerated wound healing, burn healing, and generally reduced inflammation.8,9,14

    Given that our society suffers from “inflammatory” diseases like diabetes and cardiovascular disease, academic institutions are now funding human trials on the matter. Most recently, a study published in 2021 showed that diets rich in fermented foods significantly decreased molecular signs of “unhealthy” inflammation in humans, reducing a whopping 19 inflammatory proteins within just 10 weeks of regular usage.5 One of these proteins is a particularly stubborn one to change, interleukin-6, and is linked heavily to severity in Rheumatoid Arthritis, Type 2 Diabetes, and cardiovascular disease.5 There isn’t a drug that’s been able to compete with that to date!

  3. Fermented foods likely support our microbiome and are GOOD FOR “GUT”. We already know a gut microbiome with an abundance of bacteria is good for our health. Fermented foods have repeatedly shown that they can make it to the gut intact thereby adding to its microbial diversity.2,3,7 Not only does fermentation result in a food or drink with probiotics to support the gut, it also often creates other healthy compounds like prebiotics and even gut-healthy vitamins.2 Did you know, sauerkraut was a major reason war ships fought off scurvy in WW1 because of the major boost in fermentation-produced vitamin C!!?16

  4. Fermented foods may be anti-carcinogenic. While I’m not claiming that fermented foods would ward off cancer (that study has not yet been done), it must be noted that there are dozens of studies showing that metabolites from fermentation have anti-cancer properties. Several studies have demonstrated that the lactobacillus microbe and lactic acid from fermentation suppressed early stage tumors in mice, for example, and depressed cancer development in other animals.17,18,19 In fact, many known and well-studied “anti-carcinogenic” compounds are found in fermented foods, including lactobacillus, lactic acid, and gluconic or glucuronic acid.10-12,17-19

The evidence doesn’t stop there. I could go on for chapters about the growing data on fermented foods beyond the above, including demonstrating meaningful immune boosting, cardiovascular, and metabolic benefits (there’s a LOT on diabetes to say the least). While more research needs to be done on this in humans, one thing seems clear—there’s something about fermentation that our bodies need more of.

The thing about food in general, is that adopting changes isn’t meaningful if you do it sporadically. It’s something you have to do continuously—making eating fermented foods a habit, even DAILY. In 2021, a human study showed that the more often people ate healthy fermented foods, the more benefits they saw (and the more differentiated they were from the control group), so there’s evidence to support the point.5.

As we continue to learn about these benefits, can you find a place in your diet for some more gut-health boosting fermented foods? Science is really supporting that you should. Luckily, we live in a world where so many options exist on the grocery shelf. When shopping for fermented foods, just do a little research to be sure the food is ACTUALLY fermented. If they are, you’ll see the word “fermented” on the package.

Here are a few tips to start introducing fermented foods into your diet on the daily:

  • Swap milk for probiotic yogurt in your cereal (making it sort of like a parfait)
  • Drink a kombucha for your 3pm snack instead of that cup of coffee or granola bar
  • Try miso-dressings on your salad instead of ranch
  • Put a dallop of sauerkraut on your turkey sandwich instead of lettuce
  • Mix some kimchi into your rice bowls or stir-fries (after cooking)

*Many of these studies are done on animals, not humans. It’s very expensive to do human trials, and for this reason nutrition-related studies are often limited to animal models. While this is data shows activity in a disease or health category we care about, it only SUGGESTS a benefit to humans. To consider these findings proven, would require a human trial.

  1. Dimidi, E.; Cox, S.R.; Rossi, M.; Whelan, K. Fermented Foods: Definitions and Characteristics, Impact on the Gut Microbiota and Effects on Gastrointestinal Health and Disease. Nutrients 2019, 11, 1806. https://doi.org/10.3390/nu11081806
  2. Marco, M.L.; Heeney, D.; Binda, S.; Cifelli, C.J.; Cotter, P.D.; Foligné, B.; Gänzle, M.; Kort, R.; Pasin, G.; Pihlanto, A.; et al. Health benefits of fermented foods: Microbiota and beyond. Curr. Opin. Biotechnol. 2017, 44, 94–102.
  3. Zhang, C.; Derrien, M.; Levenez, F.; Brazeilles, R.; Ballal, S.A.; Kim, J.; Degivry, M.-C.; Quéré, G.; Garault, P.; Vlieg, J.E.T.V.H.; et al. Ecological robustness of the gut microbiota in response to ingestion of transient food-borne microbes. ISME J. 2016, 10, 2235–2245.
  4. Pessione, E.; Cirrincione, S. Bioactive Molecules Released in Food by Lactic Acid Bacteria: Encrypted Peptides and Biogenic Amines. Front. Microbiol. 2016, 7, 74.
  5. Wastyk HC, Fragiadakis GK, Perelman D, Dahan D, Merrill BD, Yu FB, Topf M, Gonzalez CG, Van Treuren W, Han S, Robinson JL, Elias JE, Sonnenburg ED, Gardner CD, Sonnenburg JL. Gut-microbiota-targeted diets modulate human immune status. Cell. 2021 Aug 5;184(16):4137-4153.e14. doi: 10.1016/j.cell.2021.06.019. Epub 2021 Jul 12. PMID: 34256014.
  6. Silva, K.R.; Rodrigues, S.A.; Filho, L.X.; Lima, A.S. Antimicrobial activity of broth fermented with kefir grains. Appl. Biochem. Biotechnol. 2009, 152, 316–325.
  7. Santos, A.; Mauro, M.S.; Sanchez, A.; Torres, J.; Marquina, D. The Antimicrobial Properties of Different Strains of Lactobacillus spp. Isolated from Kefir. Syst. Appl. Microbiol. 2003, 26, 434–437.
  8. Rodrigues KL, Caputo LR, Carvalho JC, Evangelista J, Schneedorf JM. Antimicrobial and healing activity of kefir and kefiran extract. Int J Antimicrob Agents. 2005;25:404–408.
  9. Diniz RO, Perazzo FF, Carvalho JCT, Schneenedorf JM. Atividade antiinflamatória de quefir, um probiótico da medicina popular. Rev Bras Farmacogn. 2003;13:19–21.
  10. Sarkar S. Potential of kefir as a dietetic beverage - a review. Br Food J. 2007;109:280–290.
  11. Kubo M, Odani T, Nakamura S, Tokumaru S, Matsuda H. Pharmacological study on kefir—a fermented milk product in Caucasus. I. On antitumor activity. Yakugaku Zasshi. 1992;112:489–495.
  12. Liu JR, Wang SY, Lin YY, Lin CW. Antitumor activity of milk kefir and soy milk kefir in tumor-bearing mice. Nutr Cancer. 2002;44:183–187.
  13. Sreeramulu, G.; Zhu, Y.; Knol, W. Kombucha Fermentation and Its Antimicrobial Activity. J. Agric. Food Chem. 2000, 48, 2589–2594.
  14. de Oliveira Leite AM, Miguel MA, Peixoto RS, Rosado AS, Silva JT, Paschoalin VM. Microbiological, technological and therapeutic properties of kefir: a natural probiotic beverage. Braz J Microbiol. 2013;44(2):341-349. Published 2013 Oct 30. doi:10.1590/S1517-83822013000200001
  15. Bhattacharya, D.; Ghosh, D.; Sarkar, S.; Karmakar, P.; Koley, H.; Gachhui, R. Antibacterial activity of polyphenolic fraction of Kombucha against Vibrio cholerae: Targeting cell membrane. Lett. Appl. Microbiol. 2018, 66, 145–152.
  16. Raak C, Ostermann T, Boehm K, Molsberger F. Regular consumption of sauerkraut and its effect on human health: a bibliometric analysis. Glob Adv Health Med. 2014;3(6):12-18. doi:10.7453/gahmj.2014.038
  17. Sarkar S. Potential of kefir as a dietetic beverage - a review. Br Food J. 2007;109:280–290.
  18. Kubo M, Odani T, Nakamura S, Tokumaru S, Matsuda H. Pharmacological study on kefir—a fermented milk product in Caucasus. I. On antitumor activity. Yakugaku Zasshi. 1992;112:489–495.
  19. Den Hartigh, L.J. Conjugated Linoleic Acid Effects on Cancer, Obesity, and Atherosclerosis: A Review of Pre-Clinical and Human Trials with Current Perspectives. Nutrients 2019, 11, 370.

Today's blog is written by our very own Daina Trout, MS, MPH

Daina is not just our Co-Founder, she is also a nutritionist that has spent her adult life dedicated to finding and sharing health and wellness through food. With 2 masters' degrees in nutritional biochemistry and public health, Daina has called upon her education often while leading the way at Health-Ade - from how we make every batch of kombucha, to how we talk about gut health to consumers, to even how healthy our employee workplace is! She even writes a few blogs here and there. Happy reading! :)

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