Yogurt, kimchi, kefir, and kombucha tea may not be staples in many diets, but a recent study by Stanford School of Medicine researchers has discovered that large servings of these and other fermented foods give the immune system a big boost.

The clinical trial partially focused on fermented foods based on previous findings that these foods can help with weight maintenance and could lower the risk of diabetes, cancer, and heart disease.

“This is a stunning finding,” says Justin Sonnenburg, Ph.D., an associate professor of microbiology and immunology, in a statement. “It provides one of the first examples of how a simple change in diet can reproducibly remodel the microbiota across a cohort of healthy adults.”

Microbe Diversity and Gut Inflammation

Thirty-six healthy adults participated in a 10-week diet that included either fermented or high-fiber food. Each of the diets resulted in different effects on the gut and immune system. Larger servings of the fermented foods increased overall microbial diversity and produced stronger effects. For example, the levels of Interleukin 6, an inflammatory protein that has been linked to rheumatoid arthritis, Type 2 diabetes, and chronic stress, decreased.

“Microbiota-targeted diets can change immune status, providing a promising avenue for decreasing inflammation in healthy adults,” says Christopher Gardner, Ph.D., the Rehnborg Farquhar 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.”

“We wanted to conduct a proof-of-concept study that could test whether microbiota-targeted food could be an avenue for combatting the overwhelming rise in chronic inflammatory diseases,” Gardner adds. According to Gardner, low microbiome diversity has been linked to obesity and diabetes.

Conversely, the high-fiber diet did not result in a decreased level of inflammatory proteins and the gut microbes remained stable in all participants. “We expected high fiber to have a more universally beneficial effect and increase microbiota diversity,” says Erica Sonnenburg, Ph.D., a senior research scientist in basic life sciences, microbiology, and immunology. “The data suggest that increased fiber intake alone over a short time period is insufficient to increase microbiota diversity.”

Future Studies

The plan for future studies includes using mice to develop mechanisms that change the microbiome and lower inflammatory proteins. The researchers also want to explore whether a diet of fermented foods decreases inflammation or improves health in patients with immunological and metabolic diseases, and in pregnant women and older individuals.

“There are many more ways to target the microbiome with food and supplements, and we hope to continue to investigate how different diets, probiotics, and prebiotics impact the microbiome and health in different groups,” says Justin Sonnenburg.

The study can be found in Cell.