Go With Your Gut; Diet Influences Microbe Type In Stomach

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Main Category: GastroIntestinal / Gastroenterology
Also Included In: Nutrition / Diet
Article Date: 02 Sep 2011 - 10:00 PDT


It turns out that you have to "go with your gut" after all, or in fact, your gut goes with you and what you consume. Gut microbes play a significant, and underestimated, role in human health new research shows. In fact, you are what you eat, and people who eat a diet that's high in fats and animal proteins have a certain group of bacteria that flourish in their digestive tract, while the guts of people who eat a more plant-based, higher carbohydrate set of meals have other types.

Dr. James Lewis, a professor of medicine and epidemiology at University of Pennsylvania Perelman School of Medicine explains:

"You could see the people who consumed more animal protein and fat tended to fall into an enterotype characters by Bacteroides, whereas those who tended to have a diet high in carbohydrates [more plant-based] fell into an enterotype characterized by Prevotella."

For the study, researchers asked 98 healthy, non-obese American adults to report on their usual diet and the diet they ate in the week prior to giving a stool sample. From each sample, researchers then isolated the DNA of the bacteria present. What they found was that participants could be generally grouped into one of two categories, or "enterotypes", based on the prevalence of certain species of bacteria in the gut. People in the first group had high levels of the bacteria Bacteroides. In type 2, Prevotella was more prevalent.

Bacteroides thetaiotaomicron is a major component of the adult intestine and has been used as a useful model for the study of human-bacterial symbiosis. Its metabolic function for humans is to degrade plant polysacharides, a very essential capability for the human gut.

Additionally, it is very important during the postnatal transition between mother's milk and a diet heavily consisting of plant starches. It has been found to stimulate angiogenesis (growth of new blood vessels from pre-existing vessels) within the gut, due to a microbial signal via bacterial sensing Paneth cells. B. thetaiotaomicron benefits its host by providing sufficient absorptive ability for nutrients the microbe helps process.

Prevotella are among the most numerous microbes culturable from the rumen and hind gut of cattle and sheep, where they help the breakdown of protein and carbohydrate foods. They are also present in humans, where they can be opportunistic pathogens. Prevotella have been a problem for dentists for years. As a human pathogen known for creating periodontal and tooth problems, Prevotella has long been studied in order to counteract its pathogenesis.

In a second experiment, researchers had 10 participants, all of whom fell into the Bacteroides group, stay in a research lab for 10 days. Both groups were fed an identical diet and an identical amount of calories, with one exception: one group was put on a high fat/low fiber diet, while the other group was put on a low fat/high fiber diet.

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. This suggests that long-term dietary habits, rather than any short term changes, have a bigger impact on gut microbiota.

Justin Sonnenburg, an assistant professor of microbiology and immunology at Stanford University School of Medicine discusses potential next steps:

"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. The major question that springs from this work is, will long-term dietary change be able to move somebody out of their dietary enterotype? This study suggests that dietary change will not do it in the short term, but may require a long term change in diet and lifestyle."

Lewis adds that the findings suggest bacteria that live in the gut are sensitive to short term changes in diet, but it may take a long-term dietary change to significantly alter the types of bacteria that reside in the gut.

Now, the researchers are looking to see if these differences have an affect on inflammatory diseases of the gut, such as Crohn's, which affects 1.5 million people in the United States.

Lewis mentions:

"Crohn's disease is caused in part by the way our body responds to the microbes in our intestines."

He said children with this condition sometimes improve with special diets, and the team wants to see if these diets alter the composition of gut bacteria.

Written by Sy Kraft
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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