The human gut microbiome plays a crucial role in various diseases. A significant aspect of the chemical communication between gut bacteria and the body involves small molecules produced during food fermentation, such as acetate, propionate, and butyrate. These metabolites can regulate the immune system, aid in intestinal mucosa regeneration, and influence behavior. While these effects are recognized, the exact daily quantity of these molecules entering the human body was previously unknown.
A recent study published in Cell by researchers at ETH Zurich and Stanford University has accurately quantified the daily production of these molecules by gut bacteria. Using data on people's diets and daily stool output, they calculated bacterial turnover rates and measured how many fermentation products are produced to replace lost bacterial mass.
Cell"Our results provide a comprehensive picture of the substance exchange between gut microbiota and the host," states Markus Arnoldini, lead author. "Understanding this interaction is key to comprehending how the microbiome affects our health."
The findings also allow for calculations on how changes in diet or alterations in gut bacteria affect the molecular concentration. Dietary shifts significantly impact fermentation product levels more so than changes in bacterial composition.
For instance, in a contemporary Western diet, these fermentation products account for only 2% to 5% of daily energy requirements. In contrast, this can rise up to 10% in more traditional diets like those of the Hadza people of Tanzania.
"Precise quantification of these molecular signals is crucial for future research," says Arnoldini. "Our methods could help investigate changes related to conditions like colon cancer or inflammatory bowel disease by tracking daily doses of bacterial fermentation products."