A study from The Standford School of Medicine (published online in Cell on July 12, 2021) found that a diet rich in fermented foods enhances the diversity of gut microbes and decreases molecular signs of inflammation.
For the clinical trial, 36 healthy adults were randomly assigned to a 10-week diet that included either fermented or high-fiber foods, and the researchers evaluated how these two diets affected the gut microbiome and the immune system. The researchers gathered their insights and data by analyzing blood and stool samples collected during a three-week pre-trial period, the 10 weeks of the diet and a four-week post-diet period where the participants ate however they chose.
Foods like yogurt, kefir, fermented cottage cheese, kimchi and other fermented vegetables, vegetable brine drinks and kombucha tea were used ingested in the fermented style diet, and it was observed that these foods led to an increase in overall microbiome diversity with stronger effects happening in larger servings. The high-fiber diet included foods such as legumes, seeds, whole grains, nuts, vegetables and fruits, and it was shown that the diversity of the gut microbes in these participants remained stable.
“The data suggest that increased fiber intake alone over a short time period is insufficient to increase microbiota diversity," explained Erica Sonnenburg, PhD, senior research scientist in basic life sciences, microbiology and immunology.
Further findings on the fermented diet included four types of immune cells showing less activation, and a decrease in the level of 19 inflammatory proteins including interleukin 6, which has been linked to rheumatoid arthritis, Type 2 diabetes and chronic stress. In contrast, none of these 19 inflammatory proteins decreased in participants who were assigned the high-fiber diet.
“This is a stunning finding,” said Justin Sonnenburg, PhD, associate professor of microbiology and immunology. “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.”