Fermented foods boost gut microbiome diversity and reduce inflammation, study finds

A diet rich in fermented foods can increase the diversity of gut microbes and decrease molecular signs of inflammation, according to a new study led by researchers at the Stanford School of Medicine, US. In the study, 36 healthy adults were randomly assigned to a 10-week diet that included fermented or high-fiber foods. The two diets resulted in different effects on the gut microbiome and the immune system.Overall microbial diversity was increased by eating yogurt, kefir, fermented cottage cheese, kimchi and other fermented vegetables, vegetable brine beverages and kombucha tea, with larger servings having a more substantial effect.The study “provides one of the first examples of how a simple change in diet can reproducibly remodel the microbiota across a cohort of healthy adults,” says Justin Sonnenburg, an associate professor of microbiology and immunology at the Stanford University School of Medicine.Impacting immune statusIn addition, four types of immune cells in the fermented food group were less activated. Moreover, the levels of 19 inflammatory proteins evaluated in blood samples decreased. Interleukin 6, one of these proteins, has been linked to rheumatoid arthritis, Type 2 diabetes, and chronic stress.Click to EnlargeOverall microbial diversity in participants increased by eating fermented foods.“Microbiota-targeted diets can change immune status, providing a promising avenue for decreasing inflammation in healthy adults,” explains Christopher Gardner, the 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,” he adds.Impact of a fiber-rich dietIn participants who ate a high-fiber diet rich in legumes, seeds, whole grains, nuts, vegetables and fruits, none of the 19 inflammatory proteins decreased. On average, the diversity of their gut microbes remained stable.“We expected high fiber to have a more universally beneficial effect and increase microbiota diversity,” adds Erica Sonnenburg, a senior research scientist in basic life sciences, microbiology and immunology at the Stanford University School of Medicine.“The data suggest that increased fiber intake alone over a short period is insufficient to increase microbiota diversity.”Gut microbiomes’ impact on immunityDiet affects the gut microbiome, which can alter the immune system and overall health. Obesity and diabetes have been linked to a lack of microbiome diversity.“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,” says Gardner.Fermented foods can aid with weight management and reduce the risk of diabetes, cancer and cardiovascular disease.Previously, it was flagged that fruit and vegetables are among the easiest foods to ferment, and their well-known digestive benefits drive demand for NPD.Targeting the gut microbiomeThe findings paint a nuanced picture of the influence of diet on gut microbes and immune status.On the one hand, those who increased their consumption of fermented foods showed similar effects on their microbiome diversity and inflammatory markers. This is consistent with prior research showing that short-term changes in diet can rapidly alter the gut microbiome.On the other hand, the limited change in the microbiome within the high-fiber group dovetails with the researchers’ previous reports of a general resilience of the human microbiome over short periods.The researchers intend to study the molecular processes through which diets modify the microbiome and lower inflammatory proteins in mice.“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,” Sonnenburg concludes.By Nicole Kerr