The bacteria present in the intestines vary considerably from morning to evening and from summer to winter.
- The balance of microorganisms present in the intestines fluctuates depending on the time of day and the seasons.
- Daily changes would be caused by nutrient and water intake, as well as periods of rest and activity.
- As for seasonal variations, they could be caused by changes in light, exposure to pollen, humidity or temperature.
It would be much more dynamic than we thought. The intestinal microbiota exhibits daily and seasonal fluctuations. This was revealed by researchers from the University of California in San Diego (USA) during the congress Digestive Disease Week (DDW). To reach this conclusion, they performed a studyin which they used data from about 20,000 stool samples collected by the American Gut Project to examine their bacterial composition.
Intestinal microbiota: daily and seasonal cycles
By analyzing the time, date and location of collection, scientists found that 57% of bacterial phyla have a distinct 24-hour cycle. “For example, Actinobacteriota levels were lower in samples taken in the morning and much higher in samples taken towards the end of the day,” the authors said. According to the analysis, seasonal fluctuations were even more pronounced, for example, Proteobacteria levels consistently declined during winter and steadily increased until reaching a peak during summer. “The percentages of bacteria change dramatically. And if the proportions of each element are different, it is a different microbiome”said Carolina Dantas Machado, author of the works.
Food and sleep would be at the origin of the daily fluctuations
The team thinks diet and sleep are likely important factors in daily gut changes. Throughout the day, bacterial populations could be affected by nutrient and water intake, as well as periods of rest and activity. “Seasonal fluctuations are more difficult to explain, but changes in light, pollen exposure, humidity and temperature could contribute.”
According to Amir Zarrinpar, co-author of the study, it is still too early to integrate these results into actionable recommendations for clinicians or patients. However, he insists that researchers need to consider these kinds of fluctuations when conducting microbiota research.
Better understand the intestinal microbiota to better use it
The team hopes that this work will lead to a better understanding of the link between the microbiome and pathologies. “Many diseases (allergy, respiratory infections, infectious diarrhea) exhibit seasonal variations. Our data now suggests that all of these conditions occur in the context of a different microbiome,” said Amir Zarrinpar. “Bacteria perform many important functions, such as metabolizing the foods we eat and certain medications. The more we understand about the microbiome, the more we can understand how to best use it to influence our health,” concluded Carolina Dantas Machado.