A recent study conducted by the Department of Nutrition, Exercise, and Sports at the University of Copenhagen has significantly enhanced our understanding of gut health and the complex life of gut bacteria.
The research reveals that alterations in the intestinal environment influence both the composition and functioning of gut bacteria. This could ultimately help clarify why individuals possess different gut bacteria and likely why we have varying reactions to the same foods.
In an innovative experiment conducted in 2021, 50 participants ingested a capsule about the size of a thumb joint while having their breakfast. The capsule then traversed through the stomach, small intestine, and large intestine to gather data on pH levels, temperature, and pressure. The capsule was expelled in the feces anywhere from 12 to 72 hours later, and researchers observed that both the gut environment and the time taken to travel through the gut differ among individuals.
“We could see, for example, that it took 2 hours for the capsule to pass through the small intestine in some people and 10 hours in others. Since we already know that we absorb most of our nutrients in the small intestine, differences in the travel time in the small intestine probably have an impact on how much of the nutrients we absorb and how much passes on to the large intestine, where the gut bacteria kick in,” says Associate Professor Henrik Roager, Department of Nutrition, Exercise and Sports at the University of Copenhagen, who led the study.
Previously, researchers have primarily focused on the activity within the gut by analyzing stool samples and comparing them to the individual’s diet. However, the capsule provides a more accurate understanding of how the gut environment varies throughout the digestive tract.
“The capsule means that we can collect information that may help explain individual differences in digestion, nutrient uptake, and bowel movement patterns. This provides us with far greater knowledge than we have previously been able to obtain via dietary patterns and stool samples,” explains Associate Professor Henrik Roager.
As the capsule and food embarked on their journey through the digestive system, they first arrived in the stomach, where an acidic environment reigns. Here, the capsule detected a significantly low pH due to the potent stomach acid that expertly breaks down food. This crucial step prepares the nutrients for efficient absorption.
Next, the dynamic duo transitioned into the small intestine, where gut cells released alkaline bicarbonate to counteract the stomach acid, creating an ideal setting for nutrient absorption to occur.
The journey continued as the indigestible remnants of food and the capsule moved into the large intestine, where a fascinating process of fermentation unfolded, led by trillions of gut bacteria. These microorganisms produced fatty acids, which initially caused the pH to drop in the first section of the colon.
However, as one moves along the length of the large intestine, the pH value gradually increases as the fatty acids are absorbed through the intestinal wall and the activity of gut bacteria changes.
“The capsule registered all these changes in pH values, and we can estimate how long the food was in the different parts of the gut on the basis of the changes in pH. We know that pH is a crucial factor in bacterial growth and activity, so it made perfect sense that we could see that gut environment and pH are linked to differences in the composition and activity of the gut bacteria. This means that the environmental conditions we each have in our gut can help explain why we have different bacteria in the gut,” says Henrik Roager.
According to Associate Professor Henrik Roager, this groundbreaking research holds significant promise for shaping future nutritional guidelines.
“Our results show that we are all unique – also in our gut,” says Henrik Roager and continues: “We are used to assuming that we all digest and absorb food in the same way and to the same extent, but we can also see that this is not always the case. Our study provides further evidence that individuals react differently to food – and here, differences in our gut environment could very well play an important role.”
These results underscore the importance of gut physiology and environment in understanding the unique differences in the human gut microbiome and metabolism.
Journal reference:
- Nicola Procházková, Martin F. Laursen, Giorgia La Barbera, Eirini Tsekitsidi, Malte S. Jørgensen, Morten A. Rasmussen, Jeroen Raes, Tine R. Licht, Lars O. Dragsted & Henrik M. Roager. Gut physiology and environment explain variations in human gut microbiome composition and metabolism. Nature Microbiology, 2024; DOI: 10.1038/s41564-024-01856-x