Whether your digestive system works quickly or relatively slowly is not just a matter of daily comfort. According to a broad scientific review published in 2023 that combined data from dozens of studies, there is a clear connection between the rate of food movement in the intestine and the composition of gut bacteria, those microorganisms that influence almost every system in the body.
The microbiome, the community of bacteria that lives in the digestive system, plays a central role in health. It affects the immune system, metabolism, mood and even brain function.
The researchers sought to examine whether a basic and relatively simple factor such as the transit time of food in the intestine, known as intestinal transit time, could influence the composition of the microbiome.
To do this, they analyzed data from thousands of participants, including healthy individuals alongside those who suffered from irritable bowel syndrome, constipation or liver diseases.
The conclusion was clear. People in whom food moves quickly through the digestive system display a completely different bacterial composition from those in whom the process is slower.
What happens when it is too slow
When food remains in the intestine for a long time, bacteria have more time to break it down. This process leads to the creation of various biological products, some of which affect acidity levels in the intestine and inflammatory processes in the body.
Previous studies have already linked slow intestinal transit to conditions such as constipation, metabolic disorders, inflammatory conditions and even neurological diseases, including Parkinson’s.
In other words, when the digestive system operates slowly, it may be far more than temporary discomfort.
And what about transit that is too fast
The other extreme is also not ideal. Very rapid transit of food in the intestine does not allow sufficient absorption of nutrients and may lead to an imbalance in bacterial composition.
The researchers found that in both extreme conditions, both very slow and very fast, the diversity of gut bacteria is lower. Such low diversity is considered less healthy, as it limits the body’s ability to cope with changes and maintain balance.
Why it matters what you eat
One of the interesting insights that emerged from the study is that not only the diet itself determines the condition of the intestine, but also the rate at which it passes through it.
People with rapid transit tended to develop bacterial populations suited to a diet rich in carbohydrates and low in fat. In contrast, slower transit was sometimes linked to bacteria that utilize proteins.
The meaning is that two people can eat exactly the same food, yet their bodies will respond to it in completely different ways.
Until now, most recommendations in the field of nutrition have focused on what to eat. This study offers a new and more complex angle, which also focuses on the way the body processes food.
The researchers note that adding data on intestinal transit time made it possible to better predict the composition of the microbiome, even more than relying on dietary data alone.
How is it measured
Intestinal transit time is not something that is easy to measure on a daily basis, but there are various methods for assessment.
One of them is the Bristol scale, a diagnostic tool that ranks stool according to texture. Hard and lumpy stool indicates slow transit, while a soft or liquid texture indicates fast transit.
More advanced methods include smart capsules that are swallowed and measure their movement in the digestive system, or the use of certain substances whose exit time from the body can be tracked.
The broader implication of the findings is that in the future it may be possible to tailor medical and nutritional treatments more precisely for each person.
For example, personalized adjustment of probiotic supplements or diet according to the rate of digestive system activity may improve treatment effectiveness.
In addition, a better understanding of the connection between intestinal transit time and diseases may help in the early identification of health risks.
The important message here: The study emphasizes that the digestive system is not just a tube that transports food, but a complex and dynamic system that affects the entire body.
The rate at which food moves through it is an integral part of the health equation, and it may be one of the most important factors that until now has not received proper attention.
Ultimately, it is not only what you eat that matters, but also how your body deals with it.