A component of the intestinal microbiota 'decides' how many calories the body absorbs

A new study has found that a little-known component of the gut microbiota, which produces methane, may influence the amount of calories absorbed from food.

According to this study from Arizona State University (United States), some people's gut microbiomes produce a lot of methane, while others' produce very little. Its authors discovered that people whose gut microbiomes produce a lot of methane are especially good at unlocking extra energy from a high-fiber diet. This could explain why each individual gets a different amount of calories from the food that reaches the colon.

Researchers point out that high-fiber diets are not the culprit. People absorb more calories overall from a Western diet of processed foods, regardless of methane production. With a high-fiber diet, fewer calories are absorbed overall, but the amount varies depending on methane production.

More efficient microbiomes

With these results, the researchers suggest that they could serve as a basis for personalized nutrition.

“This difference has important implications for dietary interventions. It shows that people on the same diet can respond differently. Part of this is due to the composition of their gut microbiome,” says Blake Dirks, senior author of the study and a researcher at the Center for Biodesign for Health through Microbiomes.

The study, published in The ISME Journal, found that methane-producing microbes, called methanogens, are associated with a more efficient microbiome and greater energy absorption from food.

One of the main functions of the microbiome is to help digest food. Microbes ferment fiber into short-chain fatty acids, which the body can use as an energy source. In the process, they produce hydrogen. Too much hydrogen stops their activity, but other microbes can help keep this process going by using hydrogen.

Methanogens are hydrogen consumers. By consuming hydrogen, they create methane. They are the only microbes that produce this chemical compound.

“The human body doesn't produce methane, only microbes. So we suggest that it may be a biomarker signaling efficient microbial production of short-chain fatty acids,” says Rosy Krajmalnik-Brown, corresponding author of the study and director of the Center for Biodesign for Health through Microbiomes.

Help you lose weight

Research suggests that these microbial interactions affect the body's metabolism. The team found that increased methane production was associated with increased production and absorption of short-chain fatty acids in the gut.

In the experiment, researchers provided each study participant with two different diets. One diet contained more processed foods and little fiber. The other diet was rich in whole foods and fiber. Both diets contained the same proportion of carbohydrates, protein, and fat.

“This work highlights the importance of collaboration between clinical-translational scientists and microbial ecologists. Combining precise energy balance measurements using whole-room calorimetry with ASU’s expertise in microbial ecology made key innovations possible,” says Karen D. Corbin, co-author and research associate at the institute.

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Data from blood and stool samples measured how much energy the participants' bodies absorbed from food and tracked the activity of their microbes. The team compared data from people whose gut microbiomes produced high versus low levels of methane.

On the high-fiber diet, almost all participants absorbed fewer calories than on the processed food diet. But those whose intestines produced more methane absorbed more calories from the high-fiber diet than those whose intestines produced less methane.

According to its authors, this research lays the groundwork for future medical studies and treatments. “The participants in our study were relatively healthy. One thing I think would be worth studying is how other populations respond to this type of diet: people with obesity, diabetes, or other health conditions,” says Dirks.

Although the study participants weren't expected to lose weight during the experiment, some did lose some weight while following the high-fiber diet. The team is now interested in seeing how microbiome methanogens influence a diet intended to help participants lose weight.

“You can see how important it is for the microbiome to be personalized,” says Krajmalnik-Brown. “Specifically, the diet we so carefully designed to improve the microbiome for this experiment had different effects on each person, in part because some people's microbiomes produced more methane than others.”