The 13 Benefits of Fermented Foods and How They Improve Your Health | Chris Kresser

The 13 Benefits of Fermented Foods and How They Improve Your Health

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Fermented foods, which are being embraced by a wide range of experts from foodies to health gurus, are exploding in popularity. Fermented food consumption was up by 149 percent in restaurants, as of 2018, but more and more we’re also bringing these foods home and stocking them in our kitchens. (1) Stroll through the aisles of the refrigerated section of any grocery store today and you’ll likely see a variety of fermented foods that weren’t there a few years ago, including raw sauerkraut, kombucha, and kefir.

Benefits of fermented foods
Fermented foods have a number of health benefits. iStock/jchizhe

Far from being a passing trend, fermented foods are a time-honored component of the ancestral human diet. High-tech food preservation methods using chemical preservatives still dominate in the food industry, overshadowing traditional preservation methods such as fermentation. But fortunately, the reemergence of fermented foods signals a welcome return to a more ancestral way of eating.

With this growing interest in fermented foods, you might be wondering how these foods impact our health, and how you can best incorporate them into your diet. Read on to learn 13 benefits of fermented foods and how they improve your health, and discover delicious fermented food options you can easily incorporate into your diet. 

Nearly every culture around the world has a characteristic fermented food. Check out this article to find out why fermented foods are such a staple in an ancestral diet and learn how they benefit your health. #nutrition #optimalhealth #chriskresser

An Evolutionary Perspective on Fermented Foods

Fermented foods are foods produced through controlled microbial growth and enzymatic activity. These processes naturally transform food components, creating distinct textures, flavors, and aromas. Take an aged, raw milk cheese, for example, which starts as a liquid and ultimately becomes a solid through the stages of fermentation, its taste enriched and its appearance dramatically altered.

Anthropological research suggests that humans began to consume fermented foods early on in our history. Early hominids, we know from gene-mapping studies, developed specialized cell receptors designed to interact with metabolites made by lactic acid bacteria commonly found in fermented foods. This evolutionary milestone allowed our ancestors to broaden their diet by eating fruits that had fallen on the ground and begun to ferment. These findings suggest that our bodies have evolved to eat and obtain benefits from fermented foods. (2

Nearly Every Traditional Culture Ate Fermented Foods

The oldest intentionally fermented beverage, consisting of fermented rice, honey, and fruit, can be traced and dated to 7000 BC China. (3) Eventually, as agriculture took hold, humans started to ferment all sorts of foods, including:

  • Grains
  • Legumes
  • Meat
  • Fish
  • Vegetables
  • Fruits

Almost every culture around the world has a characteristic fermented food or selection of fermented foods. Bulgaria is often credited with introducing yogurt to the world; ancient nomadic people in the region stored raw milk in animal skins, where it underwent fermentation. The Japanese are famous for natto, a pungent fermented soybean dish. The Koreans have kimchi, and Icelanders have hárkarl, a fermented shark dish.

Historically, food was fermented as a means of preservation. Unique compounds produced during fermentation, such as antimicrobial peptides and lactic acid, inhibit the growth of pathogenic microorganisms and prevent food from spoiling. However, humans quickly realized that fermentation also had benefits beyond preservation; it could improve the tastes and textures of food and it rendered previously indigestible foods, such as cassava, into nutrient-dense sustenance.

While today, we use standardized cultures for producing fermented foods, early food fermentation was a more organic process. Foods were “inoculated” with microbes by the hands of people involved in their preparation, as well as the raw ingredients, water, equipment, and environment in which the food was prepared. (4) Today, foods can be fermented naturally via “wild fermentation,” using microbes present in the raw food or in the environment, or intentionally with specific bacterial, yeast, or fungal cultures. Foods can also be fermented with starter cultures from previous ferments, as with batches of sourdough or kombucha. Food fermentation has a rich, colorful history and is an excellent way to bring ancestral nutrition principles into your diet.

The number one driver of chronic disease is a mismatch between our genetics, our biology, and our modern lives. Realigning your diet to an ancestral template is often the most important step you can take to prevent or reverse a chronic illness—and a health coach can help with that process.

Health coaches are behavior change experts, and they excel at helping their clients change their habits and improve their health. They offer the support, empowerment, and accountability you need to set your own health goals and achieve long-lasting change. If you’re struggling to adopt an ancestral diet, including adding fermented foods, consider working with a Functional health coach. And if you’re interested in learning more about what health coaches do for a living, visit the ADAPT Health Coach Training Program.

13 Benefits of Fermented Foods on Your Health

Interest in fermented foods is largely due to their well-publicized association with gut health, and there is plenty of science to support those claims. Beyond that, there is also a growing body of research indicating that fermented foods support many other aspects of our health through a variety of mechanisms. Read on for a variety of benefits!

1. Fermented Foods Support the Gut Microbiome

As mentioned above, the impact of fermented foods on the gut microbiome has been extensively studied and documented in the scientific literature. Kefir, a fermented milk product, has significant beneficial effects on the gut microbiota, increasing concentrations of LactobacillusLactococcus, and Bifidobacteria. (5) Short-term consumption of yogurt for 42 days increases intestinal Lactobacilli. (6) A small study found that tempeh consumption increases Akkermansia muciniphila and immunoglobulin A, a molecule involved in the intestinal immune response. (7) Fermented foods such as chocolate may support gut health by supplying short-chain fatty acids and prebiotic fibers that support the growth of beneficial gut bacteria. (8)

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2. They Promote Bowel Regularity and Digestion

Regular consumption of fermented foods may support healthy bowel movements and digestion. In patients with chronic constipation, kefir improved stool consistency and frequency. (9) Yogurt also improves constipation caused by slow intestinal transit time. (10)

Certain fermented foods may also be easier to digest than their unfermented counterparts. For example, the consumption of sourdough bread has been found to result in less gas production, abdominal discomfort, and bloating and a lower breath hydrogen level compared to non-fermented bread. (High hydrogen levels are associated with small intestinal bacterial overgrowth, or SIBO, which you can read about here.) (11, 12) This may be due to the impact that sourdough fermentation has on the reduction of FODMAP levels in grains.

3. They Have Antimicrobial Properties

In addition to supplying beneficial microbes, fermented foods may help balance the gut microbiome as a whole by exerting antimicrobial effects against opportunistic and pathogenic microbes. Kefir grains have antifungal and antibacterial properties against common gut opportunists and pathogens, including: (13)

  • Candida albicans
  • Salmonella enterica
  • Salmonella typhi
  • Shigella sonnei
  • Staphylococcus aureus

Kefir may be a beneficial adjunct therapy, alongside antibiotics, for the treatment of Helicobacter pylori infection. (14) Kombucha inhibits the growth of H. pyloriEscherichia coliSalmonella typhimurium, and Campylobacter jejuni, while yogurt contains lactic acid-producing bacteria with broad antimicrobial properties. (15, 16)

4. They Lower Antinutrient Content and Boost the Nutritional Value of Foods

Fermentation has profound effects on the nutrient content of foods, reducing antinutrients (plant compounds that can diminish or block the body’s absorption of a food’s beneficial nutrients) while boosting the bioavailability of an array of micronutrients.

  • Fermentation of soybeans and grains reduces phytic acid, an antinutrient that reduces the absorption of minerals, through the action of microbial phytases, enzymes that catalyze the breakdown of phytic acid. (17)
  • Sourdough fermentation promotes the breakdown of gluten and may render gluten-containing grains less irritating and more digestible to individuals with gluten sensitivity. (18)
  • Kefir contains a bacterial enzyme called beta-galactosidase that metabolizes lactose, reducing the lactose content of the beverage.
  • Sauerkraut fermentation increases sulfur-based compounds called glucosinolates that have antinutrient effects at high doses, potentially inhibiting thyroid function, but offer antioxidant and anti-inflammatory benefits at lower dosages. (19, 20)

Fermentation also:

  • Increases the bioavailability of a spectrum of nutrients, including B vitamins, iron, zinc, and calcium by breaking down substances that inhibit their absorption, such as phytic acid.
  • Increases the acidity of dairy products, which transforms several of the micronutrients they contain, such as calcium and phosphorus, into more bioavailable forms. (21)
  • Synthesizes certain vitamins, particularly vitamin K2. Vitamin K2 can also be found in certain cheeses. (22)

5. They Support a Healthy Mood

Imbalances in the gut microbiome can contribute to mental health disorders, such as anxiety and depression, since gut dysbiosis can trigger a chronic inflammatory response. Fermented foods may support mental health by reducing levels of inflammatory microbes and decreasing gut inflammation. (23)

Food fermentation also increases the bioavailability of certain phenolic plant compounds that modulate neurotransmission. (24) Finally, probiotics in fermented foods may also act directly on the brain’s neural pathways via the gut–brain axis. This complex neural network connects the enteric nervous system of the gut with the central nervous system, including the brain.

6. They Help Cognitive Function

Could the consumption of fermented foods improve your cognitive function? Preliminary research suggests that it might! Lactobacillus pentosus, a probiotic isolated from kimchi, can inhibit drug-induced memory impairment in mice. (25) In a human trial, using functional magnetic resonance imaging, consumption of a probiotic-rich fermented milk product was found to modulate brain activity. (26) Finally, a randomized controlled trial found that a fermented soybean product significantly reduced mild cognitive impairment and increased blood levels of brain-derived neurotrophic factor (BDNF), compared to a group given a placebo. (27) BDNF stimulates neuroplasticity, our brain’s ability to reorganize and create new neural pathways.

7. They’re Great for Strong Bones

Research indicates that fermented milk products can boost bone health. Fermented milk products are rich in calcium, phosphorus, protein, vitamin D, and vitamin K2, crucial nutrients necessary for healthy, strong bones. Kefir consumption is associated with positive changes in bone turnover and improved bone mineral density. (28)

Fermented milk products also appear to help guard against bone loss associated with estrogen deficiency, suggesting that the consumption of fermented milk products may benefit bone health in post-menopausal women. (29)

8. They Promote Cardiometabolic Health

Cardiometabolic risk factors are an interrelated cluster of factors—including hypertension, insulin resistance, and unhealthy levels of low-density lipoprotein cholesterol and triglycerides—that increase your risk of experiencing cardiovascular disease, type 2 diabetes, or stroke. An abundance of research suggests that fermented foods may help lower these risk factors and promote cardiometabolic health.

  • Kefir may support healthy blood pressure through mechanisms similar to angiotensin-converting enzyme inhibitors, a class of drugs that relax blood vessels. (30)
  • Supplementation with 100 grams of kimchi (about three quarters of a cup) at each meal for 16 weeks has been found to reduce waist circumference and body mass index (BMI), while 10 days of supplemental kimchi reduced insulin resistance and blood pressure. (31)
  • Kombucha may lower blood sugar and blood lipids and lower the risk of non-alcoholic fatty liver disease by modulating hepatic lipid production and inflammation. (32)
  • Nattokinase, an enzyme from the Japanese natto, can lower the risk of blood clots. (33)

9. They Help with Weight Management

Fermented foods may promote a healthy body weight. Kimchi consumption impacts genes involved in the creation of fat cells. (34) Epidemiological research suggests that yogurt consumption is associated with a lower BMI, smaller waist circumference, and reduced body fat. (35) (Those are certainly positive findings, but just a note that such associations may be subject to the healthy-user bias, which I previously discussed in my article “Why You Should Be Skeptical of the Latest Nutrition Headlines: Part 1.”)

10. They Boost Immunity and Reduce Inflammation

Fermented foods positively impact the immune system and may lower inflammation. Probiotic bacteria found in kefir inhibit the production of immunoglobulin E, an immune molecule involved in allergic responses. (36) Kefiran, a sugar present in kefir, suppresses mast cell degranulation, meaning that kefir may help to prevent or alleviate allergies. (37) The infants of women who consumed fermented foods during pregnancy may be less likely to suffer from atopic dermatitis, an itchy inflammation of the skin associated with allergies. (38, 39)

11. They Regulate Cell Growth

Preliminary research suggests that fermented foods may help regulate cell growth and proliferation and, therefore, may play a role in cancer prevention. In in vitro studies, kombucha has selective toxic effects on colon cancer cells, while preserving the health of normal colonic epithelial cells. (40) Some kimchi-based probiotics may prevent cancerous cells from forming, while fermented beet juice can halt aberrant intestinal crypt (a type of cell) formation, often an early signal of intestinal cancer. (41, 42)

12. They Keep Skin Healthy

Fermented foods may support skin health by influencing the gut microbiome, systemic inflammation levels, and insulin signaling. For example, fermented dairy products may be a better choice than non-fermented dairy products for people with acne because fermentation significantly reduces insulin-like growth factor 1, a molecule in dairy products that increases inflammation and blemish-causing sebum production. (43, 44) Fermented foods may also benefit skin health by modulating the gut–skin axis, a network of signaling molecules that links the gastrointestinal (GI) tract with your body’s largest organ, the skin. (45)

13. They Protect Against Toxins

An emerging area in which fermented foods show promise is in enhancing defenses against and promoting the detoxification of environmental toxins. Lactobacillus species, including species commonly found in fermented foods, can bind heavy metals and move them out of the body. (46) The probiotic L. rhamnosus, found in fermented foods such as sauerkraut, reduces the absorption of organophosphate pesticides in the gut. (47) Fermentation may also reduce levels of mycotoxins in certain foods, such as grains. (48) If you are interested in fortifying your body against toxic exposures and gently removing toxins from your body, daily consumption of fermented foods may help.

Why Fermented Foods Are So Good for You: Bioactive Compounds

The health benefits of fermented foods are most commonly attributed to their probiotic content, but not all fermented foods contain viable probiotics. Still, even fermented foods with limited probiotic content offer health benefits. It turns out the health-promoting properties of fermented foods are due to a wide range of bioactive compounds and biochemical processes, beyond the presence and activity of probiotics.

Some of the critical health-promoting features of fermented foods include:

  • Bioactive peptides: Many lactic acid-producing bacteria found in fermented foods produce bioactive peptides, small organic substances formed by amino acids, and joined by peptide bonds. Some of these bioactive peptides, called bacteriocins, have antimicrobial properties. (49)
  • Phenolic compounds: Phenolic compounds are small molecules characterized by a ring-shaped chemical group called a phenol. You have probably heard of phenolic compounds called polyphenols, found in colorful fruits such as blueberries and blackberries. The fermentation process has been found to increase some beneficial phenolic compounds that have antioxidant properties and can help balance the gut microbiome. (50)
  • Reduces the antinutrient content of foods: As I mentioned, food fermentation can reduce antinutrients such as phytic acid, found in nuts and grains, by enhancing the activity of enzymes that break down these substances. (51, 52)
  • Delivers a dose of prebiotics and micronutrients: Fermented foods serve as a highly bioavailable delivery system for prebiotics and micronutrients, such as calcium. (53)
  • Enhances the digestibility of foods: Fermentation helps break down compounds in foods that can be difficult to digest, including lactose in dairy products and FODMAPs in vegetables, grains, and legumes.
  • Provides an array of probiotic organisms: Most fermented foods offer a rich source of probiotic microorganisms. (54) In addition, because of their chemical structure, most probiotics found in fermented foods are naturally protected from digestive juices in the stomach, allowing them to reach the intestinal tract intact. While the effects of foodborne probiotics appear to be temporary (as opposed to permanently altering the gut microbiome), they offer beneficial health effects while passing through the body. (55) The microbial communities in fermented foods are very complex, and many of these microbes have never been fully identified or categorized; this means that fermented foods  provide us with a more diverse array of probiotics than can be found in any probiotic supplement. (56) Even if the final food product looks and tastes the same no matter its source (for example, a jar of kimchi), the slightest differences in its production, including ingredients, environmental conditions, and types of microorganisms used in fermentation, can result in literally thousands of variations of the same fermented food.

Types of Fermented Foods

The fermented foods that many of us are familiar with today hail from all over the globe. Let’s discuss some of the most common fermented foods, their origins, and what makes them unique.

(Just a reminder that when you’re purchasing fermented foods, read labels and aim for pure, organic, unprocessed, and small-batch varieties. And for recipes to help you make your own Paleo-friendly fermented foods like yogurt, sauerkraut, and probiotic switchel, check out this article from Katie Melville.)

Yogurt

Yogurt is fermented milk acidified and thickened with the help of specific probiotic species, including Lactobacillus bulgaricus and Streptococcus thermophilus. Yogurt has been a part of the human diet for several thousand years. The word “yogurt” is derived from the Turkish word “yoğurmak,” which means to coagulate or thicken. References to the health benefits of yogurt are found in 6,000-year-old Ayurvedic texts. (57) However, it wasn’t until 1909 that the health-promoting properties of yogurt were attributed to Lactobacillus bacteria by Élie Metchnikoff, a Russian biologist. Traditionally, yogurt has been produced from the milk of a variety of animals, including cows, sheep, goats, yaks, and even camels.

At the beginning of the 20th century, yogurt was sold as a medicine in pharmacies. (58) The yogurt industry emerged shortly after that when Isaac Carasso, a Barcelona native, began producing yogurt mixed with jams. His son eventually founded Dannon (Danone) in France, and the first Danone yogurt factory opened in France in 1932.

Kefir

Kefir is a fermented milk product that originated in the Caucasus Mountains. It is slightly effervescent and sour and is fermented with kefir “grains,” a live culture made up of proteins, lipids, sugars, bacteria, and yeast. The bacteria and yeast feed off of the nutrients in the “grains,” creating a symbiotic microbial culture. (59) Kefir can be made from cow, goat, or sheep milk. It contains yeasts such as Kluyveromyces lactis and Saccharomyces cerevisiae and a variety of Lactobacillus species, including Lactobacillus kefiri.

Cheese

Cheese is a fermented milk product produced through the coagulation of the milk protein casein. During cheese production, the milk is acidified by microbes such as lactic acid-producing bacteria, and enzymes such as rennet are used to coagulate the milk. Once the dairy solids have separated, they are often pressed into a form and go through an aging process that promotes the growth of various molds. The origin of the milk, types of bacteria and mold, and the environment in which cheese is processed and aged intersect to influence the aroma, flavor, texture, and color of the cheese. While probiotic starter cultures are used to initiate cheese production, these bacteria often do not survive the long aging process. In some cheeses, such as Gouda and cheddar, small amounts of probiotic bacteria survive the aging process and are present in the final product. (60)

The origins of cheese are unknown, but there are historical accounts of cheese making throughout Europe before Roman times. (61) Traditional cheeses made with raw milk and fermented and aged over extended periods differ vastly from the industrialized cheeses made with pasteurized milk, commercial starters, and genetically modified enzymes that most people in the Western world eat today. Many processed foods that are passed off as “cheese” are not, in fact, cheese at all, such as the rubbery yellow “American cheese” your mom may have tucked into your sandwich when you were a kid.

Sauerkraut and Kimchi

Sauerkraut is a fermented cabbage dish that originated in the 4th century BC in northern China and may have been introduced to Europe by the Mongols. (62) Sauerkraut can be made with a starter culture or wild-fermented. When made with a starter culture, sauerkraut tends to be high in Leuconostoc, Lactobacillus, and Pediococcus organisms. In contrast, wild-fermented sauerkraut is more variable in composition, containing substantial amounts of Enterobacter and Pseudomonas.

Kimchi is a term used to describe a variety of salted and fermented vegetables that originate from Korea. (63) Kimchi typically contains cabbage, radishes, chili, pepper, garlic, onion, ginger, and salt. Occasionally, it also includes other ingredients such as sesame seeds, apple, and pear. Kimchi is dominated by lactic acid-producing Leuconostoc bacteria.

Fermented Soy Products: Tempeh, Natto, and Miso

Fermented soy products have long been consumed in Asia. Fermentation increases the nutritional value of soybeans, substantially reducing their antinutrient content. Tempeh is a traditional Indonesian soy product made with boiled, dehulled, and fermented soybeans. It is typically produced using a starter culture of Rhizopus oligosporus, a type of mold.

Natto is a fermented soybean dish that hails from Japan and is famous for its incredibly pungent flavor and aroma. It is fermented with a bacterium called Bacillus subtilis var. natto and is traditionally consumed as a breakfast food in Japan. Miso is a salty, rich fermented bean paste produced with the help of a mold called Aspergillus oryzae. While it can technically be made from any legume or combination of legumes, it is most often made from soybeans.

Sourdough Bread

Up until the invention of industrial yeast and quick-rise bread, bread was made through sourdough fermentation. Unfortunately, the transition away from traditional fermented sourdough bread to quick-rise bread made with instant yeast left us with a processed bread that is higher in antinutrients and more challenging to digest than its predecessor.

Sourdough bread production begins with the creation of a sourdough starter, a combination of flour and water mixed together and left open on the counter for several days. Yeast and lactic acid bacteria in the air colonize the starter, initiating the fermentation of the starter. While sourdough does not contain active probiotic cultures, it has other health benefits conferred by fermentation, including a lower glycemic index than quick-rise bread made with commercial yeast.

Kombucha

Kombucha is a fermented, slightly alcoholic, effervescent beverage made with black or green tea and sugar. The tea and sugar mixtures provide a fermentation medium for a rubbery disk-shaped “symbiotic culture of bacteria and yeast,” also known as a “SCOBY” or the “mother.” The extraterrestrial-looking SCOBY is actually a biofilm composed of numerous microbes, including the acetic acid-producing bacterium Komagataeibacter xylinus and the yeast Zygosaccharomyces bailii.

Fruit, juices, and spices are often added to kombucha to enhance its flavor. A variation on traditional kombucha called Jun kombucha uses green tea and honey as the liquid medium for SCOBY fermentation, providing additional prebiotic benefits from the honey. Kombucha is believed to have originated in China, Russia, or Eastern Europe around 220 BC. While beverages labeled as “kombucha” are widely available in grocery stores today, these processed, sugary drinks are a far cry from traditional kombucha.

Pu’er Tea

Pu’er or pu-erh tea is a fermented, strongly flavored tea produced in Yunnan, China, through microbial fermentation of Camellia sinensis leaves, the same leaves used to make green and black tea. (64) Traditionally, pu’er was aged for up to 15 years, but beginning in the 1970s, an accelerated “cooking” technique was implemented to expedite the fermentation process. High-quality pu’er tea has a rich, earthy flavor, while low-quality pu’er tea tends to taste muddy or moldy.

Wine

Wine, an alcoholic beverage produced through the fermentation of grapes, really needs no introduction. I’ve previously discussed the health benefits of moderate wine consumption, many of which can be attributed to compounds involved in the fermentation process used to produce wine. Wine is not generally considered a probiotic food, as its high alcohol content makes it inhospitable to most microbes. However, natural wine may contain some lactic acid-producing bacteria, such as Pediococcus pentosaceus. (65, 66) Most commercial wines filter out all bacteria, including any residual beneficial bacteria, and are frequently a source of other unsavory additives.

Beer

Beer is a fermented beverage produced by steeping a starch source, such as cereal grains, in water and fermenting the liquid with yeast. Before grains can be fermented into beer, they must be malted. Malting allows the cereal grain to germinate, releasing enzymes that break down the complex carbs in grains into simple sugars. The simple sugars feed the yeast, which subsequently produces alcohol. Most beer is fermented with brewer’s yeast and hops, the aromatic and bitter flowers of the Humulus lupulus plant. Beer is currently the most widely consumed fermented beverage in the world.

Chocolate

Chocolate is made from the fermented seeds of the Theobroma cacao tree native to the Amazon rainforest. After the cacao pods are harvested, the seed and pulp are allowed to spontaneously ferment. The microbes that ferment cocoa include the bacteria Lactobacillus fermentum and Acetobacter pasteurianus and four yeast species:

  1. S. cerevisiae
  2. Hortaea thailandica
  3. Hanseniaspora opuntiae
  4. Pichia kudriavzevii

While the drying and roasting of fermented cocoa beans kill off many of these microbes, an array of bioactive microbial compounds remains, imparting chocolate with its incredible flavor and aroma.

Fermented Meats

Fermented meats, such as salami, are produced through the fermentative action of lactic acid bacteria on meat. The bacteria involved in meat fermentation produce biogenic amines, organic compounds that give fermented meats their distinctive flavor profiles. (67) Many fermented meats are cold-cured, meaning they are cured without high temperatures; this means that some fermented meats can carry probiotic bacteria. However, the high salt content of many fermented meats will inhibit probiotic stability. Many fermented meats are also colonized by fungi. For example, salami is frequently coated in filamentous fungi, such as Penicillium.

While we’ve only scratched the surface of the vast array of fermented foods in our world today, I hope this brief overview of common fermented foods has piqued your interest. Next, let’s discuss some of the reasons why these foods should be a regular part of your diet.

Here’s Why You Should Eat Fermented Foods Daily

Clinical research indicates that most supplemental probiotics do not permanently colonize the GI tract; instead, they exert transient effects while passing through the gut. (68) In other words, the effect they have on the gut microbiome is not permanent. But what about probiotics found in fermented foods? Do they work differently? Some lab research suggests that certain probiotics present in fermented foods may adhere to Caco-2 cells, a line of human colorectal epithelial cells used in in vitro research on the GI system, but it is unknown whether these results apply to humans. (69)

While these findings run contrary to some of our previously held beliefs about probiotics having a long-term, if not lasting, effect on the gut, they still are helpful as we look for ways to improve our health and protect against chronic disease, particularly when we consider ancestral fermented food consumption patterns.

In many traditional cultures, fermented foods are a staple of the daily diet; daily consumption of these foods maintains a steady supply of probiotics in the GI tract, where the microbes exert their transient yet significant effects on our health. It follows that if we incorporate fermented foods into our daily diets, whether or not the probiotics permanently colonize our digestive tracts is of little consequence.

Based on this information, I think it is wise to include fermented foods in your daily diet because probiotics may exert health benefits only when consumed consistently.

When You Shouldn’t Eat Fermented Foods

Fermented foods are healthy, nutrient-dense additions to most diets. However, there are two health situations in which it may be best to avoid fermented foods temporarily:

  1. Histamine intolerance and mast cell activation disorder (MCAD)
  2. Mold illness or chronic inflammatory response syndrome

Histamine intolerance occurs when excess histamine builds up in the body, and pathways for histamine metabolism and disposal are impaired. The resultant excess of histamine can cause a variety of uncomfortable symptoms, including diarrhea, facial flushing, headaches, heart palpitations, and allergies, among other symptoms. Because many bacteria involved in food fermentation produce histamine as a byproduct (70), fermented foods tend to be high in histamine. If you are already suffering from histamine sensitivity, eating fermented foods may increase your total histamine burden, worsening symptoms. Resolving the underlying causes of histamine intolerance, such as gut dysbiosis, and lowering your body burden of histamine may allow you to gradually reincorporate fermented foods into your diet.

MCAD can cause symptoms similar to histamine intolerance. However, it is a more complicated condition that involves the aberrant activity of mast cells, immune cells that release histamine, and other inflammatory mediators. Because MCAD also increases the body’s histamine burden, fermented foods can worsen symptoms, until underlying causes of the abnormal mast cell activation are resolved.

People with mold illness may also want to avoid fermented foods, as the fermentation process can foster mold growth. You may find that you can tolerate fermented foods that contain primarily lactic acid-producing bacteria, such as sauerkraut. Conversely, you may need to avoid foods that contain mold as a part of the fermentation process, such as cheese, tempeh, miso, and fermented meats. For more on what to eat and what to avoid if you have mold illness, check out this article from Lindsay Christensen

Fermented foods are a long-standing, treasured part of ancestral diets around the world, and for a good reason: these foods offer abundant health benefits as well as flavors, aroma, and texture that can spice up our diets. I highly recommend the book Wild Fermentation by Sandor Ellix Katz if you are interested in learning more about how to make your own fermented foods at home. 

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