Fermented Foods Enhance Gut Health and Decrease Inflammation, Study Says

Fermented Foods

Researchers say a diet high in fermented foods reduced inflammatory proteins in participants, including one linked to conditions such as rheumatoid arthritis, Type 2 diabetes and chronic stress. Photo: asab974/GettyImages

“Eat your veggies.”

That was the advice we heard growing up and it’s still good advice. But for older adults especially, there’s additional advice:

“Eat your fermented veggies — and other fermented foods.”

A diet rich in fermented foods enhances gut health and decreases signs of inflammation, according to a 2021 study published in the journal Cell.

Eating foods such as yogurt, kefir, fermented cottage cheese, kimchi and other fermented vegetables, vegetable brine drinks, and kombucha led to an increase in overall microbial diversity, with stronger effects from larger servings, researchers found.

“This is a stunning finding,” said Justin Sonnenburg, an associate professor of microbiology and immunology at Stanford University School of Medicine, as quoted by Science Daily.

“It provides one of the first examples of how a simple change in diet can reproducibly remodel the microbiota.”

The small clinical trial involved 36 healthy adults. They were randomly assigned to a 10-week diet that included either fermented or high-fiber foods. The two diets resulted in different effects on both the gut microbiome and on the immune system.

It’s the effect on the immune system that’s so important for older people.

The research showed that four types of immune cells showed less activation in the fermented-food group. The levels of 19 inflammatory proteins, measured in blood samples, also decreased. One of these proteins, interleukin 6, has been linked to conditions such as rheumatoid arthritis, Type 2 diabetes and chronic stress.

“Microbiota-targeted diets can change immune status, providing a promising avenue for decreasing inflammation in healthy adults,” said Christopher Gardner, professor and director of nutrition studies at the Stanford Prevention Research Center. “This finding was consistent across all participants in the study who were assigned to the higher fermented food group.”

By contrast, none of these 19 inflammatory proteins decreased in participants assigned to a high-fiber diet rich in legumes, seeds, whole grains, nuts, vegetables and fruits.




Inflammation is so closely linked with aging that scientists have coined the term “inflammageing.”

It’s defined as a condition characterized by elevated levels of blood inflammatory markers that carries high susceptibility to chronic morbidity, disability, frailty and premature death.

Inflammageing, researchers have found, is a risk factor for cardiovascular diseases, chronic kidney disease, Type 2 diabetes, cancer, depression, dementia, and deterioration of muscle mass and strength (sarcopenia).

Even if eating fermented foods makes only a small contribution to helping control inflammageing and the diseases of aging, it’s certainly worth adding them to your diet or increasing your intake.

Fermented foods or beverages are those which are “produced through controlled microbial growth, and the conversion of food components through enzymatic action.”

They have a long and useful history in the human diet. They’re among the first processed food products consumed by humans and are valued in the cuisine of almost every culture in the world. Sauerkraut, for example, originated in 4th century BC. It’s still a popular food, found in most Canadian supermarkets and freshly made in homes and delis with German and Eastern European heritages.

“Fermented foods such as kombucha, kimchi, sauerkraut, yogurt, miso and tempeh have been part of the human diet for thousands of years,” says Fran Berkoff, a registered dietitian who has a private practice in Toronto.


How It Works


“Historically, fermentation was used to preserve perishable foods and enhance their shelf life but we now know that these probiotic-rich fermented foods have important health properties, helping fight inflammation, prevent digestive problems and much more. Besides their probiotics, most also are rich in variety of vitamins, minerals and fibre,” says Berkoff.

Foods are fermented in two ways. Some can become naturally fermented because of microorganisms that are already present in them. These include sauerkraut, kimchi and certain soy products. Other foods can become fermented when starter cultures are added to them, including kefir, kombucha and sourdough bread.

But what, you may well ask, about alcoholic drinks?

Beer, wine, hard cider, gin, vodka, tequila — they’re all fermented.

Well, yes, they are. But in alcoholic drinks, the fermentation process converts the sugar in grains, vegetables or fruits into ethanol (alcohol) and carbon dioxide through alcoholic fermentation, rather than converting it into lactate through lactic acid fermentation.

And ethanol is not so good for you.

Even kombucha, which is a fermented tea, may have small amounts of alcohol and these amounts can increase over time if the drink sits on a supermarket shelf. Some bottles of kombucha have been found to have as much alcohol as beer.


Applying the Science


Here’s how to get started with a healthy intake of fermented foods, as recommended by dietitian/nutritionist Berkoff:

Try kefir, a yogurt-like beverage you can drink as is, pour over cereal or add to a smoothie.

Kimchi, a spicy Korean side dish of fermented vegetables, goes well as an accompaniment to meat, or added to a sandwich, burger, stir fry or omelette

Stir fry tempeh and vegetables and serve over brown rice.

Or try kombucha, a sweet fermented tea drink.

Check the refrigerated section of the supermarket and look for sauerkraut that contains live organisms. If they have been heat processed (usually jarred or canned), much of the beneficial bacteria will be lost.