December 11, 2025
A large military-led clinical trial has found that an oral supplement made from hyperimmune bovine colostrum (HBC) - the active ingredient in the commercially available product Travelan® - did not significantly prevent travelers’ diarrhea (TD) among service members and civilian travelers.
Researchers from the Infectious Disease Clinical Research Program (IDCRP) at the Uniformed Services University (USU) tested whether this product, designed to block enterotoxigenic Escherichia coli (ETEC) bacteria from colonizing the gut and causing diarrhea, could keep travelers healthy.
The ETEC HBC supplement provided only 13.7% protection, far below the 35% goal and may have provided little or no benefit. The product did not lessen the severity of diarrhea in those who became sick. Among travelers with diarrhea, about 17% tested positive for ETEC, with 15% the ETEC HBC group and 27% the placebo group, a difference that was not statistically significant.
The randomized, double-blind, placebo-controlled trial enrolled 850 U.S. and U.K. military personnel and civilian volunteers who traveled to high-risk regions. Participants took either the ETEC HBC supplement or a placebo twice daily, starting two days before travel and continuing for up to 20 days. About one in four participants experienced TD, confirming how common and disruptive the condition remains.
While the product was safe and well tolerated, researchers say its limited benefit highlights the need for better preventive options.
“The ETEC HBC product did not consistently prevent diarrhea in travelers, likely due to several challenges,” said Dr. Tahaniyat Lalani, Associate Professor in Department of Preventive Medicine and Biostatistics (PMB) and Research Area Director at the IDCRP, HJF in support of USU. “One major issue is that TD can be caused by a broader range of ETEC strains, or by multiple bacteria, not just ETEC. Future solutions must offer broader protection, convenient to take and perform reliably in operational settings.”
“Food supplements such as prebiotics, probiotics, and immunoprophylactic agents may offer an alternative approach to preventing diarrhea; however, evidence from field trials supporting their effectiveness remains limited,” added Dr. David Tribble, Professor in USU’s PMB department and Science Director at the IDCRP. “The P2 trial is an important step toward identifying immunoprophylaxis solutions that can reliably prevent TD in operational settings, thereby supporting force health and mission readiness.”
Why It Matters:
TD remains one of the most common and costly health threats for deployed military personnel and international travelers alike. The IDCRP, a Department of War–supported program, continues to lead research on infectious disease prevention, diagnosis, and treatment to safeguard the health and readiness of U.S. forces. Through a global network of military sites in the U.S. and overseas, and strategic partnerships with the Academic Department of Military Medicine (ADMM), the U.K. Ministry of Defence, and leading academic institutions such as the Liverpool School of Tropical Medicine, Well-Travelled Clinic, IDCRP provides the infrastructure needed to conduct large-scale clinical trials in both operational environments and civilian travelers.
Disclaimer: The views expressed are those of the authors and do not necessarily reflect the official policy or position of the Uniformed Services University of the Health Sciences, Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., National Institutes of Health and Department of Health and Human Services, Departments of the Navy, Army, or Air Force, Department of War, the U.S. Government, Tripler Army Medical Center, Madigan Army Medical Center, Naval Medical Center Portsmouth, Naval Medical Center Camp Lejeune, Defense Health Agency and the U.K. Ministry of Defence. Mention of trade names, commercial products, or organizations does not imply endorsement by the U.S. Government. Investigators followed human subjects’ protection 45CFR46 policies.
Funding: This project was supported with federal funds from the Defense Health Agency, under awards HU00011920090 and HU00012520024.
