Travel’s Impact on Gut Health

International trips can disrupt your gut microbiome, especially after eating risky foods or drinking contaminated water.

Summer travel season is here—but so is the risk of gut trouble, including the infamous "Montezuma’s revenge", aka travellers' diarrhea.

Learn how travel impacts your gut health—and what you can do to stay (mostly) symptom-free abroad.

International travel, especially to regions with high infectious disease burdens, can significantly disrupt the gut microbiome and increase the risk of acquiring multidrug-resistant organisms (MDROs). This study followed travelers over time, analyzing stool samples throughout their stay to better understand how travel and diarrhea impact the gut. The findings reveal that while the gut microbiome is generally resilient, diarrhea accelerates microbiome disruption and raises the likelihood of MDRO colonization. Prolonged stays and antibiotics further compound this risk, emphasizing the need for awareness around travel-related microbiome changes and their potential role in spreading antibiotic resistance (Boolchandani et al., 2022).

To explore how international travel and diarrhea shape the gut microbiome, researchers studied 159 international students in Peru, collecting 718 stool samples across their stay. Using metagenomic sequencing, pathogen screening, and antibiotic resistance profiling, they found that while gut microbiota remained relatively stable overall, diarrheal episodes significantly decreased microbial richness and diversity. Samples taken after diarrhea showed lower richness compared to healthy travelers. Key influencing factors included stool consistency, pathogen presence, length of stay, and age. Further analysis of Escherichia coli strains for antibiotic resistance highlights how the microbiome can be compromised during illness, even during short-term travel, especially since toxigenic E. coli is a common cause of traveler’s diarrhea (Boolchandani et al., 2022).

Street food is a vital part of daily life in many communities, but when hygiene falls short, it can pose serious health risks. A study from Jimma, Ethiopia, revealed that nearly 40% of local street food handlers were infected with intestinal parasites or harmful bacteria like Salmonella, largely due to poor personal hygiene. Simple practices—like trimming fingernails and washing hands with soap after using the toilet—were strongly linked to a lower infection risk. Even more concerning, all bacterial isolates tested were resistant to ampicillin, a commonly used antibiotic (Gemechu et al., 2022). Ensuring routine medical screenings and promoting strong hygiene practices are essential steps to safeguard the well-being of street food vendors and their customers alike.

A large analysis from the American Gut Project found that both the source and amount of drinking water significantly influenced gut microbiome composition. People who primarily drank well water had more diverse gut bacteria, including higher levels of Dorea and lower levels of Bacteroides and Streptococcus. Meanwhile, those who drank less water overall had more Campylobacter, a potentially harmful bacterium. Interestingly, these effects were specific to the gut—oral microbiomes didn’t show the same associations (Vanhaecke et al., 2022). Not all water is equal when it comes to your microbiome, and water habits deserve more attention in microbiome studies.

Host Vulnerability: Individuals with a diverse gut microbiome are less susceptible to travel-related diarrhea. Commensal microbes serve as a first line of defense by producing antimicrobial compounds, reducing the likelihood of infection. Microbiome testing can detect certain pathogens or parasites, and it can also reveal dysbiosis.

Probiotics

Probiotics like Saccharomyces boulardii and certain Lactobacillus strains show potential in preventing travellers diarrhea, with some studies showing up to 45% protection (Giddings et al., 2016). However, evidence is mixed, and more research is needed before firm recommendations can be made.

Most individuals however, improve without intervention by a doctor. 

Surprisingly, the healthy traveler microbiome was also disrupted compared to a healthy U.S. cohort from the Human Microbiome Project (HMP). Healthy travelers had drastically fewer Bacteroidetes (0.5%) and more Firmicutes (89%) and Actinobacteria (6%) than the HMP group. While overall richness was similar, community composition was significantly different. The HMP cohort had higher abundances of several Bacteroidetes taxa (e.g., Bacteroides, Odoribacter, Parabacteroides), while the healthy travelers showed higher Firmicutes such as Streptococcus, Coprococcus, and Blautia, and more Escherichia and Bifidobacterium, indicating a disrupted, travel-associated microbiome even in the absence of symptoms (Youmans et al., 2015). Travel can cause subtle but significant changes to the microbiome, even in the absence of noticeable symptoms.