What is fermentation?
Fermentation is a chemical process in which carbohydrates are converted to acid or alcohol in an anaerobic (absence of oxygen) environment. Microorganisms, such as bacteria and yeast, are necessary for this process. Yeast performs fermentation by consuming sugar and producing alcohol as a byproduct. Bacteria assists by converting carbohydrates into lactic acid, which lowers the pH of the food, lengthens shelf-life, and enhances flavor. (19)(23) Cultures around the world have used the fermentation process for thousands of years for its health benefits and food preservation effects. For example, sauerkraut, a type of fermented cabbage, originates back to the fourth century B.C. and still continues to be widely consumed in Germany, Europe, and the United States. (9) Fermented foods and beverages account for nearly one-third of the world’s food intake. (6) Asian countries have consumed fermented fish, grains, legumes, and vegetables throughout history. (31) Japanese adults have a decreased risk of developing type 2 diabetes compared to Western countries, a trend associated with the population’s regular consumption of fermented soy products, such as miso and natto. (27)(24) Fermentation should not be confused with pickling. Although fermentation is a type of pickling, general pickling does not produce the same health benefits. Pickling involves soaking food, such as onion or cucumber, in an acidic brine, whereas fermenting depends on the actions of yeast and bacteria to break down the starches in the food. (27)Health benefits of fermented foods
Below are some of the evidence-based health benefits of consuming fermented products.Improves gastrointestinal health
Fermented foods and beverages contain beneficial live bacteria, commonly known as probiotics. The gut hosts trillions of microbes responsible for breaking down food, protecting the body from harmful pathogens, and supporting the immune system. Disease, stress, and certain medications (e.g., antibiotics) can disrupt the gut microbiome. Probiotics, like those found in fermented foods, may help restore balance in the gut. (27) Fermenting certain foods may also result in a reduction of fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs). FODMAPs are poorly absorbed in the small intestine and are fermented by bacteria in the large intestine, which may contribute to gas, bloating, diarrhea, and constipation. Foods high in FODMAPs may be problematic for individuals with irritable bowel syndrome (IBS) as they can induce or aggravate intestinal symptoms for these individuals. (21) Furthermore, research has shown that several yeast strains, particularly S. cerevisiae and T. delbrueckii, may degrade up to 90% of fructans, a type of oligosaccharide, in wheat bread after proofing (fermenting) for four hours. (10)(39) This is good news for individuals with IBS who may not typically tolerate wheat in their diet.Helps support healthy immune function
Approximately 70% of your body’s immune cells reside in the gut. Fermented foods support the immune system by maintaining a healthy gut microbiome. (35) Probiotics found in fermented foods may lessen the duration of acute upper respiratory infections such as the common cold. (12) Fermentation also increases antioxidant activity in foods, which protect immune cells from oxidative stress. (15) Additionally, several studies have shown that the bacteria in kefir, a fermented dairy beverage, may support the immune system by stimulating immune cells, such as macrophages, needed to fight infection. (36)(1) Consuming kefir may also help alleviate symptoms, such as airway inflammation, associated with allergies and asthma. (5)(14)Increases nutrient content and bioavailability
The fermentation process increases the bioavailability of some dietary nutrients, including B vitamins, calcium, iron, magnesium, and zinc. This is believed to be a result of a reduction in phytic acid, a compound found in plants that may impair nutrient absorption. (25)(30) Fermentation also breaks down cell walls of plant foods, making it easier for your body to digest and absorb nutrients. (37)(25) Furthermore, fermentation may reduce or remove sugars from some foods. The process involved in making kombucha, a fermented tea, requires the use of sugar and a biofilm of bacteria and yeast called a scoby. Sugar feeds the scoby, and as the kombucha ferments, sugar concentration in the tea decreases. (11)May lower the risk of heart disease
Regularly consuming fermented dairy products, such as kefir and yogurt, may decrease your risk of developing cardiovascular disease. (38) Research has shown that fermented dairy may increase serum HDL levels (healthy cholesterol) and may play a role in preventing hypertension (high blood pressure). (33)(32)(18) One study also showed that consuming large amounts (210 g per day) of fermented cabbage, known as kimchi, for seven days significantly reduced serum total cholesterol and LDL levels (unhealthy cholesterol) compared to the group that consumed only small amounts (15 g per day). (7)May help prevent and manage type 2 diabetes
Certain fermented foods may positively impact blood glucose levels and contribute to the management of type 2 diabetes. The probiotics found in fermented products may reduce the inflammatory response in individuals with diabetes, resulting in improved insulin sensitivity. (26)(29) Research has shown that consumption of fermented products, such as kefir and sauerkraut, may complement an existing treatment plan for diabetes management. One study demonstrated that daily consumption of kefir significantly reduced hemoglobin A1c (HbA1c), an indicator of blood sugar control. (29)(26) Animal studies suggest that kombucha, a fermented tea, may also reduce hemoglobin A1c. (29) Furthermore, kimchi may be effective in reducing fasting blood sugar, which is elevated in type 2 diabetes. One study determined that consuming large servings of kimchi significantly reduces fasting blood sugar by 6.96%. (7)May influence mood
There appears to be a theoretical link between mental health and the consumption of fermented foods. Improved bioavailability of nutrients in fermented foods, particularly B vitamins such as folate and B12, may improve mood and reduce symptoms of depression and anxiety. (3)(8)(30) Folate and vitamin B12 are necessary for serotonin and dopamine production, which are mood-regulating neurotransmitters. (22)(34) Furthermore, the positive impact fermented foods have on the health of the intestinal microbiota may also improve vitamin D levels. (28)(16) Vitamin D deficiency is associated with symptoms of depression and anxiety in certain individuals. (17)(2)Did you know? Research has shown that kefir, a fermented dairy beverage, contains more than 50 strains of bacteria and yeast, which promote the growth of healthy microbes in the gut. (5)(20)
Types of fermented foods and beverages
Fermented products are widely available and can be found in most grocery stores. Some common fermented foods and beverages include:- Kefir: yogurt-like dairy beverage
- Kimchi: seasoned, fermented cabbage common in Korean cuisine
- Kombucha: probiotic-rich tea
- Miso: fermented soybean paste
- Sauerkraut: fermented cabbage
- Tempeh: fermented soybean cake
- Yogurt: fermented milk (27)
Adding fermented foods to your diet
Current dietary guidelines don’t explicitly state recommendations for fermented foods; however, incorporating these foods into your diet on a daily basis may benefit your health. (4) Adding fermented products into your diet is simple — it can be as easy as adding sauerkraut to your sandwich or drinking kefir with your breakfast. Enjoy a variety of fermented foods and beverages and find the products you like best. Keep in mind that not all fermented foods contain probiotics. Some fermented products, such as beer and wine, undergo a process that eliminates any remaining microorganisms. Furthermore, heating fermented foods can deactivate microorganisms. (27) There currently is no regulatory requirement for companies to indicate microbial levels on their products; however, many brands voluntarily provide this information. With the rising popularity of fermented foods, more companies are choosing to be transparent about their products via food labels. When shopping for fermented products, search for products that contain live microorganisms. (27) Many fermented foods, including kombucha and sauerkraut, release bubbles when opened, which is a good indicator that the product contains live organisms. (9)The bottom line
Consuming fermented foods and beverages is a simple and practical way to add more probiotics to your diet. Regular consumption of fermented products, such as yogurt and kombucha, may improve digestion, lower your risk for heart disease and diabetes, and support your immune system. (21)References
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