The Impact of International Travel on Gut Health: Insights from a New Study

International travel is increasingly being recognized for its influence on gut health, beyond just the spread of infectious diseases. A study, titled “Human Gut Microbiota Composition Associated with International Travels,” explores how traveling affects the gut microbiome, showing that both the diversity and composition of gut bacteria can change significantly depending on where a person travels and their health status.

Researchers conducted the study using two groups: a longitudinal cohort of travelers who gave stool samples before and after their trips, and a comparative cohort of travelers, migrants, and non-travelers. The main goal was to see if extended stays in non-European countries affected the diversity and makeup of gut microbiota. The researchers also wanted to identify which types of bacteria were more prevalent among travelers.

More details on the study’s two main cohorts are below:

1. Longitudinal Cohort: This group included 17 individuals from Catalonia who provided stool samples both before and after spending more than three months in non-European countries. Their microbiota was analyzed to compare changes pre- and post-travel.
2. Cross-sectional Cohort: This group included 84 travelers and migrants who had recently returned or moved to Catalonia from non-European countries. Their gut microbiota was compared to 97 non-travelers who had not left the country in the past year.

Methodology

• Participants collected their own stool samples following strict guidelines, using a standardized transport system.
• The microbiota was analyzed through 16S rRNA gene sequencing to identify different bacteria.
• Statistical analyses were done to compare the diversity and composition of the microbiota among pre- and post-travel samples, as well as between travelers, migrants, and non-travelers.

Results

In the longitudinal cohort, bacterial diversity increased after travel, though this increase was not statistically significant. However, when comparing travelers and migrants to non-travelers, a notable association between travel and greater gut microbiota diversity was found. Travelers had a higher presence of bacterial genera such as Escherichia/Shigella, Bacteroides, and Parabacteroides.

The analysis also revealed three distinct clusters of bacterial composition, with clear differences between travelers and non-travelers. Two specific clusters stood out in travelers:

1. One cluster, characterized by a high abundance of Escherichia/Shigella, was linked to lower microbial diversity and richness.
2. Another cluster, dominated by Faecalibacterium and Bacteroides, exhibited the highest levels of diversity and richness, suggesting a healthier gut microbiome.

The study showed that international travel could have a substantial impact on gut microbiota. For example, travelers returning from places like South America often saw an increase in microbial diversity.

However, a subgroup of travelers had a less diverse gut microbiota dominated by Escherichia/Shigella, a pattern linked to traveler’s diarrhea and antimicrobial resistance. This low-diversity profile is concerning because it can lead to gut imbalances and potential health issues like inflammation, chronic infections, and an increased risk of gastrointestinal diseases.

On the other hand, some travelers experienced an increase in beneficial bacteria like Faecalibacterium, known for promoting gut health and reducing inflammation. This suggests that travel can have both positive and negative effects on gut microbiota, depending on factors like the traveler’s health status and environmental exposures, including diet and contact with new microbial environments.

Conclusion:

The study highlights the dual effects of international travel on gut health. While some travelers experience increased gut diversity, others may develop imbalances dominated by harmful bacteria. These findings underscore the importance of considering gut health when traveling, particularly for people with pre-existing conditions or weakened immune systems.

The use of probiotics might help reduce the risks of low gut diversity during travel, but further research is needed to understand how diet, travel conditions, and destination environments influence changes in gut microbiota.

Another key takeaway from the study is the role of the gut microbiota in traveler’s diarrhea, a common issue for those visiting low-resource regions. Strengthening gut microbiota before traveling, possibly through diet or probiotics, could help prevent negative health outcomes related to imbalances in gut bacteria.

Additionally, identifying specific bacterial genera associated with healthy or unhealthy gut profiles opens up the possibility for personalized treatments.

Reference:

Henares D, Monsalvez V, Brotons P, et al. Human gut microbiota composition associated with international travels. ScienceDirect. July 31, 2024. Accessed September 20, 2024. https://www.sciencedirect.com/science/article/pii/S1477893924000632.