WARNING!
This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.
Traditionally, fermented foods are a simple strategy to affect and optimize the health of your gut. Fermented foods are teeming with beneficial microbes that are sadly lacking in many Americans’ diets. Nearly every culture has a recipe for fermented food that has been passed down through the generations.
Kimchi has a long tradition in Korea where it's served as a side dish with most meals.1 Cabbage and radish are the two most popular vegetables used in the preparation of kimchi, but some family recipes also use cucumber, onion and carrot as the primary vegetable.
The flavor and microflora of kimchi are impacted by additional ingredients such as garlic, salt and fermented fish sauce. Most Korean families have their own recipes, which are closely guarded secrets.2 Yet, the nature of the process of fermenting means that no two batches ever taste exactly the same. In addition to the ingredients, the temperature and length of fermentation contribute to the flavor of the finished product.
Originally, fermenting cabbage and other common vegetables to make kimchi was a way of preserving fresh vegetables for the winter months.3 Although it is available commercially, you can easily experiment at home with your own vegetables to develop a flavor and nutritional profile you enjoy.
While the flavor will vary depending upon the ingredients you use, most kimchi is sour and spicy. If you use garlic during fermentation, the flavor and taste of the vegetable will intensify.
As it has become more popular, it can be found in the refrigerated section of many grocery stores or purchased at Asian markets and sushi bars. Because it's made with vegetables and fermented it contains an ample amount of fiber and is rich in microbes that help feed a healthy gut.
Importance of Probiotic Foods to Your Health
Foods rich in beneficial bacteria act as probiotics. Using a probiotic supplement or eating fermented foods has become increasingly popular as evidence mounts that probiotics have a beneficial effect on the bacterial communities residing in your gut.4
The most common bacteria found in probiotics are from the lactobacillus and bifidobacterium groups.5 Information from the 2012 National Health Interview Survey showed approximately 4 million adults in the U.S. had used probiotics or prebiotics in the 30 days leading up to the survey.6
Recent information published in 20197 also recorded approximately 3.9 million people regularly take probiotic supplements with the expectation that they will help improve digestion and immune function, prevent heart disease and improve mental health.
Food manufacturers have recognized the benefits of eating probiotic foods and have incorporated this in their advertising, especially for fermented dairy foods like yogurt. However, store-bought yogurt brands are also high in sugar, which feeds harmful bacteria in the gut. In this case, the disadvantages far outweigh the advantages of consuming probiotics from store-bought yogurt.
The production of kimchi is accomplished by fermenting vegetables with lactic acid bacteria (LAB), the same bacteria used in fermenting yogurt.8 This group of bacteria is one of the most significant groups of probiotics, demonstrating a high survival rate in test conditions and resistance to low pH indicating reasonable tolerance to bile.9
Probiotics Benefit Leaky Gut and Inflammation
Although some bacteria can cause disease, there are nearly 100 trillion of them living in your gut, which are collectively called the gut microbiota.10 What exists in your gut is a balance of harmful and beneficial bacteria that contribute to your body’s control of the inflammatory response.11
When the bacteria in your gut are out of balance it increases the permeability of the membrane lining your intestinal wall. This is referred to as leaky gut. The tiny gaps allow undigested food, bacteria and metabolic waste to enter your bloodstream, which sets up an inflammatory response in your body.
This inflammation also confuses the immune system and increases the risk for an autoimmune attack.12 Leaky gut syndrome has been associated with inflammatory bowel diseases like Crohn's disease and ulcerative colitis. However, even healthy people can have varying degrees of intestinal permeability that can lead to a variety of health symptoms.
Kimchi plays two roles in protecting your gut health. In the first place, it is a rich source of probiotics helping to reseed your gut microbiota with healthy, beneficial bacteria. Kimchi is also high in insoluble fiber, which is the preferred source of nutrition for beneficial microbes.
Research from the University of California13 has shown the microbial balance in the gut microbiota is driven in part by the intestinal tract’s ability to limit resources to harmful microbes when beneficial microbes are given adequate nutrition. In addition to helping to close intestinal permeability, beneficial bacteria produce short-chain fatty acids as a byproduct of metabolism.14
These fatty acids signal the cells in the large bowel to limit the amount of oxygen within the large intestines. Beneficial bacteria are anaerobic and don't survive well in an environment high in oxygen. This is another pathway in which the microbiota and your intestinal cells collaborate to promote a cycle that maintains gut health.
The signaling pathway can malfunction when beneficial bacteria are not provided adequate nutrition. If you eat a diet high in sugar and carbohydrates, it feeds the harmful bacteria. This both increases the oxygen level and intestinal permeability and makes your body more susceptible to aerobic enteric pathogens, such as E. coli and salmonella.
Animal studies have also indicated that probiotics can help reduce inflammation and improved the physical functioning of the intestinal tract in older mice.15 The researchers found a probiotic cocktail “could ameliorate age-related leaky gut and inflammation, hence opening up novel avenues to explore and exploit the clinical utilities of such therapeutic regimens.”16
Your Gut Health Impacts Disease Risk
Protecting your gut health can also reduce your disease risk. Scientific evidence has demonstrated that many conditions and diseases, such as learning disabilities, diabetes, obesity and Parkinson's disease, are influenced by your gut microbiome. One review published in 2020 goes so far as to say that most inflammatory diseases begin in the gut.17
Dr. Alessio Fasano,18 a pediatric gastroenterologist, researcher and director of the Center for Celiac Research and Treatment, points out that there are simply not enough genes to account for the high number of chronic diseases that affect humans.
Genetics also cannot explain the timing of the disease onset. Instead, he suggests that it's important to look at the gut microbiome as “it is the interplay between us as individuals and the environment in which we live that dictates our clinical destiny.”19
Evidence has shown that exposure to bacterial overgrowth and gluten are the two most powerful triggers to stimulate the production of zonulin by intestinal epithelial cells.20 Zonulin is a family of proteins that are a biomarker for gut permeability. Activation of the pathway may be a defense mechanism to remove bacterial overgrowth or changes in composition (dysbiosis) or both.
Kimchi can help protect against bacterial overgrowth and thus limit the activation of the zonulin pathway. Chronic inflammatory diseases that have been associated with dysregulation of this pathway include autoimmune and metabolic disorders, intestinal diseases and neuroinflammatory diseases.21
In other words, you can affect the potential risk and reduce the symptoms of health conditions far outside your gut when you take care of your gut microbiome by providing a diet rich in probiotics and nutrition to feed your beneficial bacteria.
Gut Health May Improve Sleep and Support Your Immune System
Researchers have discovered there is a curious bidirectional link between your gut and your sleep habits. Two studies shed light on this connection. The first was published in Frontiers in Psychiatry22 and focused on the role that your gut microbiome plays in insomnia and depression. The authors wrote:23
“There is considerable evidence showing that the gut microbiome not only affects the digestive, metabolic, and immune functions of the host but also regulates host sleep and mental states through the microbiome-gut-brain axis.
Preliminary evidence indicates that microorganisms and circadian genes can interact with each other. The characteristics of the gastrointestinal microbiome and metabolism are related to the host's sleep and circadian rhythm."
As noted in the paper, there is mounting research that suggests your gut microbiome affects your sleep cycle through what's known as the gut-brain axis. According to the authors, this happens through three different pathways, all of which use a bidirectional flow.
In a second study,24 researchers investigated how your sleep affects the microbes in the gut, which we already know have far-reaching effects on your general health and the strength of your immune system.25 Using advanced sleep measuring devices, the quality of a participant’s sleep was measured and then compared to the composition of their gut microbiome to see if a correlation could be made.
The researchers found that diversity was positively correlated with sleep efficiency and total sleep time. They also found several bacterial groups that were negatively correlated with sleep quality indicating there is a link between the composition of your gut microbiome, sleep physiology and your immune system.
In addition to supporting your sleep hygiene, a healthy gut may also protect against viral infections, such as severe COVID-19 disease.26 In a review27 of more than 1,000 patient records, researchers found that those who presented on admission to the hospital with GI symptoms and suspected COVID-19 infection had worse outcomes than those who did not have GI symptoms.
Even after adjusting for comorbidities, demographics and other clinical symptoms, the results held. You can read more about the links between COVID-19 and your gut microbiome in “A Healthy Gut to Help Combat COVID.” One of the researchers from Rush University spoke with a journalist from MedPageToday, saying:28
"We knew that GI symptoms could be part of the infection but we did not know if they made a difference and conferred higher risk. So we wanted to look into the impact of initial GI symptoms to see if they might coincide with more serious disease and we found that those with GI symptoms also had established risk factors for severity, such as older age, diabetes, obesity, and hypertension."
More Kimchi Benefits
In addition to the probiotic benefits from kimchi, the nutritive content has also been extensively studied. Researchers have found the dish is high in vitamins A and C along with 34 amino acids.29 The major carotenoids reported are lutein and beta-carotene in a variety of concentrations that are related to the agricultural practice, harvesting and fermentation methods used.
Depending on the raw materials, kimchi may also be high in calcium, magnesium, potassium and sodium. The most important bioactive compounds are phytochemicals that have been prized for their medicinal potential with antiobesity, anticancer and anti-atherosclerotic properties.
Researchers have focused on the polyphenolic contents of kimchi as it relates to health claims that include protective effects against a variety of different types of cancer, neurodegenerative diseases and cardiovascular disease. Many of the raw materials are important sources of dietary phytochemicals, including onions, which are a source of flavonoids, including quercetin.
Animal studies have demonstrated antiobesity actions as it relates to the animal size, weight and inflammatory response from fat tissue. Other studies have shown kimchi can help balance cholesterol, triglycerides and low-density lipoprotein cholesterol levels.
Regular consumption may help to reduce the potential for metabolic syndrome and balance high blood pressure. Fermentation appears to boost the benefits of the raw materials used in kimchi to improve metabolic parameters with antiaging effects.30
The LAB bacteria, dominant in the fermentation of kimchi,31 appears to reduce or eradicate putrefactive and pathogenic bacteria that may be present in the process. This helps to increase the functionality of the food and contributes to the large number of health benefits found in research, including the effects on obesity, cancer and colorectal health.
Control Quality by Making Your Own Fermented Vegetables
Some people start out making fermented foods for health benefits and then get hooked on the flavor or vice versa. Kimchi has a high level of beneficial bacteria that are ideal for optimizing your gut flora, and it is high in fiber to help nourish those bacteria. Eating one-quarter to one-half cup of fermented veggies with one to three meals each day can have a dramatic impact on your health.
If you're new to fermented foods, introduce them gradually, beginning with as little as 1 teaspoon of kimchi with a meal. Observe your reactions for a couple of days before adding another small portion and increase your dose gradually as your body can tolerate.
While cabbage is the main ingredient in traditional kimchi, other common elements include mustard greens, garlic, ginger root, Asian radish and Korean chili powder.
It is surprisingly easy to make your own kimchi at home, which allows you to tweak the recipe to suit your taste and to control the quality of the ingredients. You can find recipes for homemade kimchi in “The Tangy Tasty Superfood Korean Families Eat with Every Meal” and “Join the Kinetic Culture and Make Your Own Fermented Vegetables.”