Fermented foods can improve digestion, boost the immune system and reduce inflammation.jchizhe/Getty Images
Food fermentation isn’t new. It’s been used for thousands of years to preserve foods, as well as to enhance their taste and texture.
More recently, though, fermented foods have gained the attention of researchers and consumers for their potential health benefits.
This past November, for example, the Canadian Fermented Foods Initiative officially launched in London, Ont., bringing together scientists, health professionals, chefs and food producers to help Canadians better understand the health benefits of fermented foods.
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Fermented foods can improve digestion, strengthen the immune system and reduce inflammation. Evidence also suggests that eating them regularly may help improve metabolic health and potentially guard against chronic disease.
Here’s what to know about fermented foods – what they are, the evidence for their health benefits and ways to add them to your diet.
What are fermented foods? Do they contain probiotics?
Fermented foods and beverages are made by adding beneficial bacteria, yeasts and moulds to a food source to break down, or ferment, its sugars and starches. During fermentation, compounds such as organic acids or alcohol are created, which preserve foods and create unique flavours and textures.
The fermentation process can also add gut-friendly live bacteria to foods such as yogurt, kefir (a yogurt-like drink), buttermilk, kombucha (a fermented tea), unpasteurized sauerkraut, kimchi, fermented vegetables, unpasteurized tempeh, miso and natto (fermented soybeans).
Kombucha, a fermented tea, can be consumed as an alternative to soft drinks or carbonated flavoured water.alvarez/Getty Images
Fermented foods don’t necessarily contain “probiotic” bacteria, though. To be deemed a probiotic, live bacteria strains must be scientifically demonstrated to deliver a specific health benefit when consumed in adequate amounts.
Many fermented foods don’t use bacterial strains with proven health benefits. Some brands of yogurt and kefir, however, may contain probiotics that have been added after fermentation.
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Even so, fermented foods with live bacteria that aren’t true probiotics still provide gut health benefits.
Some fermented foods, on the other hand, don’t contain any live microbes such as bacteria and yeasts.
For example, fermented foods such as pickles and sauerkraut may undergo pasteurization to kill potential pathogens and extend shelf life. The baking process for sourdough bread kills the yeast and bacteria used in fermentation.
To find fermented foods with live bacteria, look for “contains live and active cultures” or “fermented with naturally present cultures” on labels.
Health benefits of fermented foods
Even without live bacteria, the fermentation process can break down compounds, making certain vitamins and minerals, as well as lactose, easier to digest and absorb. Microbes can also produce B vitamins and vitamin K2 during fermentation.
As well, fermentation creates new beneficial compounds, such as organic acids and peptides (short chains of amino acids) that have anti-inflammatory and antioxidant effects.
And by introducing beneficial gut microbes, fermented foods can encourage a more diverse and robust gut microbiome which, in turn, can help support immune health and reduce inflammation.
A 2021 study from Stanford University found that a daily diet high in fermented foods led to an increase in microbial diversity and a reduction of inflammatory markers in the bloodstream.
Fermented dairy products are the most studied fermented foods.
Observational studies and randomized controlled trials have consistently tied a higher daily yogurt intake, even in moderate amounts, to improved insulin sensitivity and a lower risk of metabolic syndrome, prediabetes and Type 2 diabetes.
Unsweetened yogurt can be added to both sweet and savoury foods.Drazen Zigic/Getty Images
Kefir may improve blood sugar control, blood vessel function and low-density lipoprotein cholesterol, as well as reduce inflammation, but more research is needed.
Evidence also hints that kombucha, fermented vegetables and fermented soy foods may support metabolic health.
A review of 16 randomized controlled trials, published in Frontiers in Nutrition in 2025, concluded that fermented foods, in particular fermented milk, was associated with improvement in overall IBS symptoms. (In some people, though, fermented foods may trigger IBS symptoms.)
Research also suggests that consuming fermented foods may reduce perceived stress levels.
How to add fermented foods to your diet
If you’re new to fermented foods, introduce them gradually to give your digestive system time to adjust.
Eating fermented foods daily, or almost daily, is ideal for maintaining their microbial benefits since live bacteria and yeasts colonize the gut transiently, not permanently.
That means their beneficial gut effects will diminish if you don’t consume fermented foods regularly. Consistency is key.
Include a variety of fermented foods in your diet to provide different types of beneficial bacteria and nutrients.
For example, unsweetened yogurt can be added to both sweet and savoury foods. Use it as a base for smoothies and salad dressings. Replace mayonnaise with it to make tuna, salmon and egg salad. Top hot cereal, chili or stew with a dollop of yogurt.
Try unsweetened kefir in place of milk in smoothies and overnight oats. Or pour it over granola and muesli.
Add kimchi, unpasteurized sauerkraut or unpasteurized pickles to whole grain bowls, sandwiches, burgers and stir-fries. Or serve them as a condiment to grilled meat and egg dishes. Look for refrigerated versions with live cultures.
Fermented vegetables such as kimchi may support metabolic health.4kodiak/Getty Images
Toss cubes of unpasteurized tempeh into salads, bowls and stir-fries. Or crumble it and add to tacos.
Try kombucha as an alternative to soft drinks or carbonated flavoured water. Choose unpasteurized (refrigerated) brands and ones lower in sugar.
Fermented foods aren’t a magic bullet. As part of an overall healthy diet, though, they can support good health.
Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan.