The dietary change did impact bacteria levels in the gut, the study found, but not enough to move the Bacteroides group into the Prevotella group.
That suggests that long-term dietary habits, rather than any short term changes, have a bigger impact on gut microbiota, Lewis said.
The next step for researchers is getting a better handle on how the bacteria that resides in our gut may influence the development of disease, said Justin Sonnenburg, an assistant professor of microbiology and immunology at Stanford University School of Medicine. He praised the researchers for being able to correlate specific enterotypes with actual human diets.
Though no one has yet proven a cause-and-effect relationship, researchers have linked altered microbiota with many diseases and conditions, including obesity, inflammatory bowel disease, irritable bowel syndrome and potentially colorectal cancer.
What's almost certain is that gut microbes play a significant -- and underestimated -- role in human health, he added.
One theory is that our immune systems may react to certain bacteria in the gut, triggering an inflammatory response that could contribute to several diseases, Lewis said.
"There's also a whole another line of research that's looking into to what extent the bacteria living in our intestines is related to the host's risk of becoming obese, perhaps by influencing the efficiency of absorbing nutrients," he said.
It's known that the bacteria living in the gut help humans harvest energy from the food we eat. If the bacteria there are really good at that, some people may be getting more calories from a given food that others, he theorized.
Prior studies in mice have shown that if you transplant the bacteria in the intestines from an obese animal to an ordinary mouse, t
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