A recent study enhances our understanding of the gut and the role of gut bacteria. It reveals that alterations in the gut’s environment can influence both the composition and the activity of gut bacteria. This could ultimately shed light on the variations in gut bacteria among individuals and why we may respond differently to the same foods.
A recent study from the Department of Nutrition, Exercise and Sports at the University of Copenhagen enhances our understanding of the gut and the functioning of gut bacteria. The findings indicate that changes in the gut environment affect both the composition and activity of gut bacteria. This insight may clarify why we all have distinct gut bacteria and why individuals often react differently to identical foods.
An Exploration of the Gut
In 2021, a group of 50 participants swallowed a capsule approximately the size of a thumb joint during breakfast. This capsule traveled through the stomach, small intestine, and large intestine, gathering data on pH levels, temperature, and pressure. After 12 to 72 hours, the capsule was expelled in the feces, revealing significant variability in both gut conditions and transit times among individuals.
“For example, we observed that the capsule took as little as 2 hours to traverse the small intestine for some and as much as 10 hours for others. Given that most nutrient absorption occurs in the small intestine, these differences in transit time likely affect how much nutrition is absorbed and how much reaches the large intestine, where gut bacteria become active,” explains Associate Professor Henrik Roager from the University of Copenhagen, who spearheaded the study.
Traditionally, gut activity has been monitored through stool samples correlated with dietary intake. The capsule, however, provides a more accurate understanding of how the gut environment evolves through the digestive process.
“The capsule allows us to gather data that can elucidate individual variances in digestion, nutrient absorption, and bowel movement patterns. This leads to a better understanding than what we previously had from analyzing diet and stool samples combined,” says Associate Professor Roager.
Understanding the Gut Environment: From Acidic Stomach to Alkaline Small Intestine
Upon entering the digestive system, the capsule’s first stop is the stomach, where a very low pH is recorded due to the release of acid that helps in food breakdown. Next, the food and capsule travel to the small intestine, where gut cells produce alkaline bicarbonate to neutralize stomach acid, facilitating nutrient absorption.
The indigestible leftovers and capsule then move to the large intestine, where gut bacteria ferment the food, producing fatty acids that initially lower the pH in the colon. Over the length of the large intestine, the pH gradually rises as these fatty acids are absorbed into the gut wall and the activity of gut bacteria shifts.
“The capsule documented all of these pH changes, allowing us to estimate the duration food spent in various gut sections. Since pH is a key factor in bacterial growth and activity, it was logical that we could observe the link between gut environment, pH levels, and the variations in gut bacteria composition and activity. This suggests that the unique conditions within each person’s gut may help account for differences in gut bacteria,” says Henrik Roager.
Personalized Nutrition
According to Associate Professor Henrik Roager, the insights gained from this study could significantly inform future dietary guidelines.
“Our findings highlight that each individual is unique—especially within their gut,” states Roager, adding, “We often assume that everyone digests and absorbs food uniformly, but it’s evident that this is not necessarily true. Our research provides further evidence that individual responses to food can vary, and variations in our gut environment likely contribute to this,” he explains.
The results demonstrate the significant influence of gut physiology and environment on the differences observed in the human gut microbiome and metabolism.
Study Highlights
The capsules swallowed by the 50 participants measured 26 x 13 mm. All subjects ingested the capsule alongside a standardized breakfast that included rye bread with butter and jam, a boiled egg, a plain yogurt with nuts and blueberries, and a glass of water.
The research was led by Nicola Procházková, who was a PhD student and postdoc at the Department of Nutrition, Exercise and Sports at the University of Copenhagen from 2020-2024. The findings are detailed in the scientific article titled “Gut physiology and environment explain variations in human gut microbiome composition and metabolism,” published in the journal Nature Microbiology. This study was conducted in collaboration with researchers from DTU Food and KU Leuven in Belgium, and is part of the Challenge project PRIMA.
The research received support from the Novo Nordisk Foundation.
