According to researchers at Wroclaw Medical University, long-distance travel can disrupt not only the body’s biological clock but also the circadian rhythms of the bacteria inhabiting the gut.
The researchers state that this phenomenon—sometimes referred to as “jet lag”—can temporarily alter the composition and activity of the gut microbiota and contribute to digestive issues.
In a review published in the journal Nutrients, scientists from Wroclaw Medical University examined existing research on the impact of long-distance travel on circadian rhythms, the gut microbiome, and overall bodily function.
They focused specifically on athletes who frequently cross time zones for competitions, but noted that their findings may also apply to tourists, airline crew members, shift workers, and others who regularly alter their sleep and eating schedules.
When people rapidly cross multiple time zones, their internal biological clocks cannot instantly adapt to the new day-night cycle. This results in jet lag, which can cause sleep problems, fatigue, reduced concentration, and digestive disturbances.
However, this disruption can also affect the trillions of microorganisms residing in the digestive tract.
The composition and activity of gut microbiota fluctuate throughout the day and depend on factors such as meal timing. When a traveler suddenly begins eating, sleeping, and experiencing daylight at different times, the circadian rhythms of both the body and its gut microbiota can be temporarily disrupted.
The gut microbiota may continue to follow the daily schedule of the point of departure while the traveler’s body adapts to the conditions at the destination. Research indicates that this temporary disruption can alter the microbiome’s composition and reduce the production of short-chain fatty acids, such as butyrate, propionate, and acetate. These compounds—produced when gut bacteria break down dietary fiber—help maintain the intestinal barrier and play a vital role in metabolism and immune function.
However, researchers emphasize that the microbiome is not the sole cause of digestive issues following long-distance travel.
Dehydration, stress, reduced physical activity, and abrupt dietary changes can also contribute to constipation, bloating, a sensation of heaviness, and changes in appetite.
The review suggests several ways travelers can mitigate the effects of jet lag, including gradually adjusting sleep schedules before departure and carefully managing exposure to daylight.
Adjusting meal times in advance to align with the destination’s schedule—an approach known as “chrono-nutrition”—and maintaining adequate hydration can also be beneficial.
“A sudden change in meal times directly affects digestive enzyme secretion, bile production, and gastrointestinal motility. Consequently, the balance of gut microbiota may temporarily shift toward less favorable bacterial strains. This can slow intestinal transit, leading to constipation and digestive problems,” says study co-author Laura Raffner.
The researchers also discuss melatonin, noting that its effectiveness depends on the timing of administration. Taking it at the wrong time—without considering the direction of travel or arrival time—can prove ineffective and even shift the body’s biological clock in an undesirable direction.
According to the researchers, shift workers, those who frequently alter their sleep schedules, and individuals experiencing other circadian rhythm disruptions may face similar effects. They may be particularly important for athletes who increasingly have to compete in grueling international events.
The authors cite the 2026 FIFA World Cup as an example. The tournament takes place across a region spanning six time zones, meaning players must contend not only with long-distance travel but also with changes in daylight duration, climate, and other environmental conditions.
“Evidence suggests that travel-induced changes in sleep, stress levels, and environmental conditions lead to measurable shifts in the diversity and activity of gut microbiota, which can impact health and athletic performance,” the authors write.
The researchers argue that personalized strategies—combining the regulation of light exposure, sleep, and meal timing with approaches to support the gut microbiome—could ultimately help athletes prepare for competitions away from home.
However, they emphasize that further research is needed to determine how knowledge regarding circadian rhythms and gut microbiota can be transformed into effective strategies for preparing travelers and athletes for long-distance journeys.
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