Fermented vs. high-fiber diet microbiome study delivers surprising results
Investigating the relationship between diet, gut bacteria and systemic inflammation, a team of Stanford University researchers has found just a few weeks of following a diet rich in fermented foods can lead to improvements in microbiome diversity and reductions in inflammatory biomarkers.
The new research pitted a high-fiber diet against a diet with lots of fermented food. Thirty-six healthy adults were recruited and randomly assigned one of the two diets for 10 weeks.
“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,” explains Christopher Gardner, co-senior author on the new study.
Blood and stool samples were collected before, during, and after the dietary intervention. Over the course of the trial the researchers saw levels of 19 inflammatory proteins drop in the fermented food cohort. This was alongside increases in microbial diversity in the gut and reduced activity in four types of immune cells.
Perhaps most significantly, these changes were not detected in the group tasked with eating a high-fiber diet. Erica Sonnenburg, another co-senior author on the study, says this discordancy between the two cohorts was unexpected.
“We expected high fiber to have a more universally beneficial effect and increase microbiota diversity,” she says. “The data suggest that increased fiber intake alone over a short time period is insufficient to increase microbiota diversity.”
One hypothesis raised in the study to explain the different responses to the two diets is that fiber-induced microbiota diversity increases can take longer to manifest than fermented food-induced changes. Several biomarker changes were noted in the fiber diet cohort, including altered short-chain fatty acid production and increased stool microbial protein density. The researchers note these are indications high-fiber diets can remodel gut microbial populations but potentially at a slower rate than fermented foods.
“It is possible that a longer intervention would have allowed for the microbiota to adequately adapt to the increase in fiber consumption,” notes Sonnenburg. “Alternatively, the deliberate introduction of fiber-consuming microbes may be required to increase the microbiota’s capacity to break down the carbohydrates.”
Perhaps the biggest takeaway from this new study is the rapid immune and microbiome changes induced by the fermented diet and the consistency of responses across the whole cohort. Justin Sonnenburg, another researcher working on the project called the findings a “stunning” demonstration of how a small dietary change in healthy adults can influence microbial diversity and subsequent immune activity.
The next step for the researchers will be to move to animal studies and explore what specific mechanisms are mediating these dietary-induced changes. Plus, the researchers are also curious about whether a combined high-fiber and fermented food diet enhances these responses.
“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 new study was published in the journal Cell.
Source: Stanford Medicine