Fermented Foods and Their Benefits: Miso, Yogurt, and More
People have consumed fermented foods for tens of thousands of years. Recent scientific research now finds evidence of their importance to the human diet.
This article will discuss fermented foods, their health benefits and risks, and how to select fermented foods. It will also answer some frequently asked questions about fermented foods.
Fermentation is the process by which microorganisms, such as bacteria and yeast, break down food to produce energy when no oxygen is present. This process produces carbon dioxide, alcohol, organic acids, and bioactive compounds. As such, fermented foods are nutritionally and functionally rich products.
Additionally, the process may impede the growth of other, less beneficial microorganisms, allowing the foods to have a longer shelf life.
Many fermented foods contain probiotics, which are beneficial microorganisms that can improve health. Probiotics can aid in the growth of beneficial microbes while reducing harmful microbes. Therefore, they can offer positive impacts on health, such as:
- aiding digestion and nutrient absorption
- improving symptoms of gastrointestinal (GI) conditions, such as irritable bowel syndrome (IBS) and colic
- decreasing the frequency of infections
- supporting immune system health
Consuming fermented foods may increase gut microbiome diversity and reduce inflammation. Conversely, low gut microbiome diversity has links to chronic diseases, such as obesity and type 2 diabetes.
Fermented foods are also a rich source of nutrients, phytochemicals, and other bioactive compounds. The gut microbiome plays a pivotal role in health and disease.
Below are some further examples of fermented foods and their health benefits.
Learn more about how probiotics work and their benefits.
Kefir is a fermented drink made by adding kefir grains to milk or water. Some producers may also enrich it with important minerals, vitamins, and other nutrients.
A 2021 review suggests that kefir may help strengthen the immune system against viruses and reduce inflammation.
Research also suggests it may improve bone health in people with degenerative conditions, such as osteoporosis.
However, the findings vary, which may be due to the different microorganisms present in each product. Some commercial kefir brands may only contain negligible amounts of probiotics. As such, it is important to read the label and check its probiotic content to gain the most benefits.
Different types of kefir are available in stores, such as kefir made from:
- nondairy milk, such as coconut, oat, and cashew milk
- sheep, goat, or cow milk
- coconut water
Several studies show that consumption of yogurt and other fermented foods may:
- improve GI health
- improve lactose malabsorption
- treat infectious diarrhea
- reduce the duration and number of respiratory infections
- enhance immune and anti-inflammatory responses
A 2020 meta-analysis suggests that eating yogurt may link to a reduced risk of conditions such as cardiovascular disease and type 2 diabetes.
Yogurt is commercially available in dairy milk or nondairy milk formulations, such as coconut, oat, rice, or cashew beverages.
Fermenting sourdough bread improves its nutritional value in several ways.
The fermentation of sourdough bread significantly increases its levels of nutrients while reducing certain antinutrients. Sourdough is rich in polyphenols, flavonols, and vitamin C.
Kimchi is a traditional Korean side dish that comprises varying combinations of salted fermented vegetables, ginger, garlic, and fish sauce. It commonly includes vegetables such as:
- napa cabbage
- carrots
- radish
- scallions
Data suggests that kimchi and other pickled vegetables may have benefits such as:
- having anti-obesity, antidiabetic, and antihypertensive properties
- acting against the buildup of plaque in the arteries
- increasing beneficial gut bacteria levels, which may improve symptoms of conditions such as IBS
Research also indicates that the probiotic strain predominant in kimchi correlates with a modest reduction of body fat in people with obesity.
Sauerkraut is a salted and fermented cabbage dish that is particularly rich in beneficial bacteria.
A small, randomized trial observes that those with IBS experienced improved symptoms when they consumed sauerkraut.
A later study suggests that the isothiocyanates in cabbage become more concentrated through fermentation. Small clinical trials suggest that isothiocyanates may offer benefits to help symptoms of autism spectrum disorder and cancer.
However, as the sizes of these studies are very small, larger-scale investigations are necessary to confirm the effects.
Try eating sauerkraut as a side dish or in salads and sandwiches.
Tempeh, or tempe, is a high protein food that is traditional in many parts of Asia. It typically consists of fermented soybeans, though it sometimes contains other added beans and whole grains.
Natural soybeans contain some antinutritional factors that can reduce the gut’s absorption of important nutrients. However, the fermentation process reduces the antinutritional factors present in soy, making the food more nutritious.
A study of tempeh’s health benefits in animal and human cells suggests that benefits may include:
- antioxidant properties
- gut microbiome and health improvements
- immune system function improvements
- cognitive function support
- peptides that offer additional health properties, such as antioxidant, antimicrobial, and antihypertensive action
Tempeh is also a relatively affordable, high quality source of protein. You can steam or fry it and add it to your favorite dish as a meat replacement.
Natto is a traditional Japanese food that also comes from fermented soybeans. Making natto includes cooking soybeans for several hours before adding the bacteria culture. After that, the mixture ferments at about 100–120°F for 22–24 hours.
Natto is rich in vitamin K2, which is important for bone health and reducing the calcification of arteries.
Additionally, a higher intake of natto may correlate with lower rates of cardiovascular disease deaths.
You can add natto to any dish, although many traditionally eat it with rice.
Miso is a traditional Japanese food. This thick, fermented paste comes from soybean koji, which is soybeans inoculated with the Aspergillus oryzae mold. Koji is a term for any grain or legume on which people cultivate A. oryzae for fermentation. The three most common types of koji are rice, barley, and soybean koji.
Koji-based fermentations contain enzymes that may aid in digestion.
Research in Japan shows that increased consumption of some fermented soybean products may reduce mortality rates in males and females (sex assigned at birth).
Many people traditionally drink miso as soup. However, you can add it to broths and sauces to flavor other dishes.
Kombucha is a fermented beverage that involves adding bacterial cultures to a mixture of sugar and tea. It can contain high concentrations of beneficial bioactive compounds, antioxidants, and antimicrobial agents.
Animal and test tube studies report the beneficial effects of kombucha. However, there is currently limited human evidence to support those claims.
Some people brew kombucha at home under unsterile conditions, increasing the risk for contamination. This can lead to illness, with reports of home-brewed kombucha causing:
Some commercial kombucha can be very high in added sugar. Be sure to check the label for its added sugar content.
Not all pickles are fermented, but some are. Quick pickles, a common type of pickle in grocery stores, are not fermented. Instead, they use an acid, such as vinegar, in their brine.
Fermented pickles undergo a curing process that adds probiotics and additional nutrients.
Adding pickles to sandwiches and salads or eating them as a snack is a great way to add them to your diet.
Fermented foods carry a risk of contamination when processed in an unsterile environment or with improper tools. Additionally, some fermented foods are susceptible to contamination from potentially toxic or poisonous substances, such as:
- pathogens
- bacterial toxins and harmful bacteria strains, such as Staphylococcus and Streptococcus
- histamines
If you are sensitive to histamines or unsure whether fermented foods are safe for you, contact your doctor or a licensed nutritionist.
The World Health Organization (WHO) states that probiotics must meet certain criteria. They must:
- have an accurate identification
- be safe for the intended use, such as a food product being safe for consumption
- have at least one positive human clinical trial supporting its use and safety
- be alive in the product at an effective dose during its shelf life
To optimize health benefits from fermented products, check the following details when making a purchase:
- added sugar content, particularly in products such as:
- kefir
- kombucha
- yogurt
- kimchi
- expiration date
- manufacturing date
Labels often state the amount of colony-forming units (CFUs) at the time of manufacture, referring to the probiotic cell count. Most probiotic strains decline throughout their shelf life. As such, the closer you purchase a fermented product to its expiration date, the more CFUs it may have lost. This means older probiotic products may be less beneficial.
Additionally, the process of pasteurization kills the bacteria that make fermented foods so beneficial. As such, choose products with labels that specify that they are unpasteurized.
Other frequently asked questions
Imashi Fernando M.S., R.D.N., has reviewed the following frequently asked questions.
What are the benefits of fermented foods?
Fermented foods can increase beneficial bacteria in your gut and compete with harmful bacteria.
They can have a wide range of health benefits, including:
- improving GI health
- improving immune function
- regulating weight
- improving mood
- reducing inflammation
- improving nutrient absorption
What are the best fermented foods for gut health?
Probiotic strains and other beneficial compounds differ between fermented foods. As such, consuming diverse fermented foods will provide various probiotics and nutrients, helping you receive multiple benefits.
Research suggests that having more diverse gut bacteria correlates with better health.
Many fermented foods and beverages are rich sources of probiotics. Fermentation often increases the nutritional content of food while reducing factors that inhibit nutrient absorption. They may also regulate gut bacteria and health.
Examples of fermented foods include kefir, yogurt, and fermented soybean products, such as miso and tempeh.
However, there can be much variability in probiotic composition and quantity in different products. Additionally, home-fermented foods can risk contamination.
Contact your doctor if you want to change your diet for health concerns.
