PHILADELPHIA—Like the humans they live in, gut bacteria appear to have a preference for certain types of diets. Some bacteria, it seems, prefer guts that host a protein-rich meat-based diet; others prefer a more carbohydrate-heavy, vegetarian-like environment. Researchers from the Perelman School of Medicine at the University of Pennsylvania found an association between long-term dietary patterns and the bacteria of the human gut. In a study of 98 healthy volunteers, the research team used diet inventories and compared that to sequenced DNA from stool samples. The sequencing allowed the researchers to count and identify gut bacteria. Fecal bacterial communities clustered into two broad groups, or enterotypes, distinguished primarily by levels of Bacteroides and Prevotella.
The enterotypes were strongly associated with diet, particularly protein and animal fat (Bacteroides genus) versus carbohydrates (Prevotella genus). Both Bacteroides and Prevotella are broad genera of bacteria species that typically live in the human gut. Humans tend to have mostly a species from one bacterial group but not both. Vegetarians were more likely to be in the Prevotella group, the enterotype associated with diets enriched in carbohydrates and lacking meat, and the one vegan was also in the Prevotella group.
Subsequently, 10 healthy volunteers were enrolled in a controlled feeding experiment in which their diets were fixed for a 10-day period. All ten subjects in the controlled-feeding experiment were in the Bacteroides group at the start, during, and at the end of the experiment. Their gut microbiomes changed within one day but stayed within the same broad Bacteroides group, even if they ate a diet high in carbohydrates over the 10-day period, emphasizing the short-term stability of the enterotypes.
There are several potential applications of this research. The Penn investigators are currently exploring the relationship between dietary therapies for Crohn’s and the composition of the gut microbiome.
“It’s well known that diet strongly affects human health, but how diet influences health is not fully understood," says Frederic D. Bushman, PhD, professor of Microbiology. “We found that diet is linked to the types of microbes in the gut, which provides a potential mechanism connecting diet with health."
