Fermented food diet increases microbiome diversity and reduces inflammation, study finds – ScienceDaily

In a clinical trial, 36 healthy adults were randomly assigned to a 10-week diet that included either fermented or high-fiber foods. The two diets had different effects on the gut microbiome and the immune system.

Consumption of foods such as yogurt, kefir, fermented cottage cheese, kimchi and other fermented vegetables, vegetable brine drinks, and kombucha tea has resulted in an increase in overall microbial diversity, with increased levels of microbial diversity. stronger effects from larger portions. “It’s an amazing discovery,” said Justin Sonnenburg, PhD, associate professor of microbiology and immunology. “This provides one of the first examples of how a simple diet change can reproducibly reshape the microbiota in a cohort of healthy adults.”

Additionally, 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.

“Diets targeted to the microbiota may alter immune status, offering a promising pathway to reduce inflammation in healthy adults,” said Christopher Gardner, PhD, professor at Rehnborg Farquhar and director of nutrition studies at Stanford Prevention Research Center. “This result was consistent among all study participants who were assigned to the highest fermented food group.”

Stable microbial diversity in a high fiber diet

In contrast, none of these 19 inflammatory proteins decreased in participants on a diet high in fiber, high in legumes, seeds, whole grains, nuts, vegetables and fruits. On average, the diversity of their gut microbes also remained stable. “We expected that the high fiber content would have a more universal benefit and increase the diversity of the microbiota,” said Erica Sonnenburg, PhD, senior researcher in basic life sciences, microbiology and immunology. “The data suggests that increasing fiber intake alone over a short period of time is insufficient to increase microbiota diversity.”

The study will be published online July 12 in Cell. Justin and Erica Sonnenburg and Christopher Gardner are co-lead authors. The lead authors are Hannah Wastyk, a doctoral student in bioengineering, and former postdoctoral researcher Gabriela Fragiadakis, PhD, who is now an assistant professor of medicine at UC-San Francisco.

There is ample evidence that diet shapes the gut microbiome, which can affect the immune system and overall health. According to Gardner, low microbiome diversity has been linked to obesity and diabetes.

“We wanted to conduct a proof-of-concept study that could test whether foods targeted to the microbiota could be a way to combat the overwhelming increase in chronic inflammatory disease,” Gardner said.

Researchers have focused on fiber and fermented foods due to earlier reports of their potential health benefits. While high-fiber diets have been linked to lower death rates, consuming fermented foods can help with weight maintenance and may reduce the risk of diabetes, cancer, and cardiovascular disease.

The researchers analyzed blood and stool samples taken during a three-week pre-trial period, the 10-week diet and a four-week post-diet period when participants ate as they had. selected.

The results 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, in line with previous research showing that short-term changes in the diet can alter quickly. the gut microbiome. On the other hand, the limited change in the microbiome within the high fiber group is consistent with previous reports by researchers of general resilience of the human microbiome over short periods of time.

Design a suite of dietetic and microbial strategies

The results also showed that higher fiber intake resulted in more carbohydrate in stool samples, indicating incomplete breakdown of fiber by gut microbes. These findings are consistent with other research suggesting that the microbiome of people living in the industrialized world is depleted of fiber-degrading microbes.

“It is possible that a longer intervention allowed the microbiota to adapt adequately to the increased fiber intake,” said Erica Sonnenburg. “Alternatively, the deliberate introduction of fiber-consuming microbes may be necessary to increase the microbiota’s ability to break down carbohydrates.”

In addition to exploring these possibilities, the researchers plan to conduct studies in mice to investigate the molecular mechanisms by which diets alter the microbiome and reduce inflammatory proteins. They also aim to test whether foods high in fiber and fermented work synergistically to influence the microbiome and immune system of humans. Another goal is to examine whether the consumption of fermented foods decreases inflammation or improves other health markers in patients with immunological and metabolic diseases, as well as in pregnant women and the elderly.

“There are many other ways to target the microbiome with foods and supplements, and we hope to continue to investigate the impact of different diets, probiotics and prebiotics on the microbiome and the health of different groups,” said Justin Sonnenburg. .