Eating Fermented Foods Both Fights Inflammation and Boosts Immunity, According to a New Study

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Packed with live probiotics (aka good gut bacteria), fermented foods have long been the darlings of dietitians thanks to their many microbiome-balancing benefits. Studies have shown that eating the probiotic strains that thrive in these naturally tangy foods (such as yogurt, sauerkraut, and kimchi) can boost your overall intestinal and respiratory health and even slash your risk for chronic conditions like type 2 diabetes and heart disease.

But until now, there was limited research to show exactly how. Thanks to a new study conducted by researchers at Stanford University, we’re now learning that the benefits of fermented foods may be tied to their ability to combat signs of chronic inflammation in the body.

Experts In This Article
  • Hannah Wastyk, Hannah Wastyk is a PhD student at Stanford in the bioengineering department. Her research interest lies in studying the microbiome and how it relates to the immune system in human studies through machine learning and statistical methods.

To analyze the relationship between fermented foods and inflammation, the researchers randomly assigned 36 healthy adults a ten-week meal regimen that was either rich in fermented foods (including yogurt, kefir, kimchi, vegetable brine, and kombucha) or rich in fibrous foods, like vegetables, legumes, whole grains, nuts, and seeds. Because both food groups have been shown to support gut health and immunity in the past, they were curious whether the benefits of fermented foods or those of fibrous foods alone would reign supreme.

“In order to help participants implement these dietary changes in a lasting, sustainable way, the dietitians gave them a guide to each type of food and then allowed them to eat whatever foods within that category that they liked and could find at their grocery store, just directing them to eat six servings total each day,” says Hannah Wastyk, lead author on the study and a PhD student at Stanford in the bioengineering department.

Throughout and after the ten week period, the researchers tracked a whole slate of over 230 different markers of inflammation, and found a striking difference: Across the board, those people who ate the fermented foods showed a decrease in 19 different inflammatory proteins circulating in their blood, while those who ate the fiber-rich diet didn’t show that downward trend at all.

People who ate the fermented foods showed a decrease in 19 different inflammatory proteins circulating in their blood, while those who ate the fiber-rich diet didn’t show that downward trend at all.

What’s more, the researchers also investigated the activity of various immune cells and found that four of them showed less activation among the fermented-food eaters (signaling a less-stressed immune system), in comparison to the same cells in the fibrous-food eaters.

“The reason why we looked at so many different metrics is because we wanted to see that broader inflammatory and immunity trend, and whether it was going up or down,” says Wastyk, “because we know that higher levels of chronic inflammation are present with chronic diseases—so, on the flip side, less overall inflammation reflects a better immunity profile.”

Interestingly, the dip in inflammation did show up in a few metrics for certain people within the fiber-eating group—but only those individuals who already had a higher level of microbiome diversity (aka a gut filled with different types of bacteria) when the study began. “Those people likely already had more of the fiber-digesting bacteria flourishing within their microbiomes, so that may be why they experienced a drop in inflammation from eating the fiber diet alone,” explains Wastyk.

The takeaway? Eat both fermented foods and foods with plenty of fiber.

If your gut microbiome isn’t in a well-balanced, diverse place already, the results of this study suggest that eating a fiber-rich diet alone may not be enough to see that drop in inflammation that the researchers found with the fermented-food eaters. Your best bet? Working both beneficial food groups into your diet. (If you don’t consume much of either food group as-is, just ease in and apply moderation to avoid any stomach or digestive issues.)

Luckily, there are many fermented foods that already contain plenty of fiber, too. Try kimchi, sauerkraut, tempeh, and any other form of pickled fruit or vegetable. You can also toss your next salad or roasted veggie platter in a miso-based dressing, or make a smoothie from a combination of fruit and kefir for a healthy dish or drink that checks both boxes. We're particularly partial to Lifeway Kefir, which packs 12 probiotic strains, 11 grams of protein, and 30 percent of your daily calcium needs per serving, and comes in a variety of delicious flavors.

Bottom line: If you eat fermented foods in order to increase your microbial diversity and also eat fiber to fuel all those different microbes, you could have a synergistic benefit that’s even larger than what we found in the study, says Wastyk. Consider the two groups partners in their gut-healthy, inflammation-reducing efforts—with fermented foods perhaps leading the charge.

To learn more about how fermented foods impact gut health, watch this video:

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