"Start a probiotic a week before you fly" is one of the most repeated travel tips out there. The research is more mixed than the advice suggests, and which probiotic you take matters more than when you start it.
Written by Vita Globe Editorial Team | Reviewed against CDC guidance, expert travel-medicine guidelines and peer-reviewed research
Should you take probiotics before traveling?
If probiotics are already part of your routine, keep taking them. But don't count on them to prevent traveler's diarrhea. A 2007 meta-analysis found a modest benefit, mainly for two specific probiotics[3], and a later expert panel concluded there's insufficient evidence to recommend commercially available probiotics for prevention[4]. Effects are strain-specific[2], so results from one product don't transfer to another.
Caveat: There are no good studies on the best time to start a probiotic before travel; "one week before" is a convention, not a finding.
Sources: McFarland 2007 · Riddle 2017 · NIH ODS: probiotics · Verified 2026-09-28
In this article
What do probiotics actually do?
Probiotics are live microorganisms that, in adequate amounts, provide a health benefit, according to an international scientific consensus definition[1]. The important part of that definition is that the benefit has to be shown, and it's shown for specific strains at specific doses.
The NIH makes the same point: the effects of probiotics can be specific to certain strains, and recommendations need to be strain-specific[2]. That's why "probiotics prevent travel sickness" is too broad a statement to be useful.
Do probiotics prevent traveler's diarrhea?
The honest answer is: not reliably enough for experts to recommend them.
- A 2007 meta-analysis of 12 trials found an overall 15% relative reduction in risk, with the clearest results for Saccharomyces boulardii and a combination of Lactobacillus acidophilus and Bifidobacterium bifidum[3].
- A 2017 expert panel on traveler's diarrhea concluded there is insufficient evidence to recommend commercially available prebiotics or probiotics to prevent or treat it[4].
- The CDC's current travel guidance also says data are insufficient to recommend them, noting small studies and inconsistent products[5].
What does work better? Food and water precautions and, for some people, bismuth subsalicylate[5]. Our guide to avoiding traveler's diarrhea covers the details.
What about travel constipation?
There's no research on probiotics for travel constipation specifically. In a 2014 meta-analysis of trials in adults with chronic constipation, probiotics improved gut transit time, stool frequency and consistency on average, with Bifidobacterium lactis showing the most consistent results[6]. The authors cautioned that the studies varied a lot and had risk of bias, and that effects depended on the species[6].
So a probiotic may be one supportive piece of a regular routine, but water, fiber, movement and a consistent schedule do most of the work. See Travel Constipation: Why It Happens and How to Prevent It.
If you want to take one, how should you do it?
- Start at home, not at the airport. There's no evidence on ideal timing, but starting early means any gas or mild tummy changes happen before your trip, not during it. The NIH notes side effects in healthy people are usually minor, like gas[2].
- Keep it consistent. Tie it to a daily habit like breakfast; see Best Time to Take Probiotics.
- Read the label. Look for named strains and follow the storage directions on the package. Our post on reading a probiotic label explains what to look for.
- Check first if you're immunocompromised or seriously ill. Probiotics are generally safe for healthy people, but the NIH notes greater concern for vulnerable groups[2].
The honest summary
- Probiotics are not a proven way to prevent traveler's diarrhea.
- Benefits are strain-specific; evidence for one product doesn't transfer to another.
- If a probiotic is part of your everyday routine, keeping it going while you travel is reasonable.
- Food and water precautions, hydration, fiber and movement matter more.
Our option
Vita Globe Gut Health To-Go Duo
The To-Go Duo pairs two resealable travel pouches: Super Probiotic Gummies, a live-culture blend that includes Bacillus coagulans and Bifidobacterium lactis (suggested use: 2 gummies once daily), and sugar-free Prebiotic Fiber Gummies, with 2g of dietary fiber per 1-gummy serving from a blend that includes FOS from chicory root. Every product in the bundle is tested by an independent third-party lab. The strains in our probiotic gummies aren't the ones studied for traveler's diarrhea, and we don't claim they prevent it. And while our blend includes B. lactis, the constipation trials used specific strains and doses, so their results can't be assumed to apply to any one product. The Duo is meant for people who already like a daily fiber and probiotic routine and want to keep it going while they travel.
Frequently asked questions
How long before a trip should I start probiotics?
There's no research-backed answer. Starting at home, early enough to know how your body tolerates it, is a practical choice.
Which probiotic is best for traveler's diarrhea?
Older trials favored Saccharomyces boulardii and a Lactobacillus acidophilus plus Bifidobacterium bifidum combination[3], but expert guidelines still don't recommend probiotics for prevention[4].
Can probiotics make travel constipation better?
Some strains improved stool frequency in trials of chronic constipation, but results varied widely[6], and travel itself hasn't been studied.
Are probiotics safe to take while traveling?
For healthy people they're generally well tolerated, with minor side effects like gas[2]. Check with a clinician if you have a weakened immune system.
Should I keep taking probiotics if I get diarrhea on a trip?
Focus on fluids and oral rehydration first, and get care for blood in the stool or fever[5]. Ask a clinician before adding or changing supplements while you're sick.
Sources
- Hill C, Guarner F, Reid G, et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11:506-514. doi:10.1038/nrgastro.2014.66
- NIH Office of Dietary Supplements. Probiotics: Fact Sheet for Health Professionals. Updated March 25, 2025. ods.od.nih.gov
- McFarland LV. Meta-analysis of probiotics for the prevention of traveler's diarrhea. Travel Med Infect Dis. 2007;5(2):97-105. doi:10.1016/j.tmaid.2005.10.003
- Riddle MS, Connor BA, Beeching NJ, et al. Guidelines for the prevention and treatment of travelers' diarrhea: a graded expert panel report. J Travel Med. 2017;24(suppl_1):S63-S80. doi:10.1093/jtm/tax026
- Connor BA, Leung DT. Travelers' diarrhea. In: CDC Yellow Book 2026: Health Information for International Travel. Centers for Disease Control and Prevention. cdc.gov
- Dimidi E, Christodoulides S, Fragkos KC, Scott SM, Whelan K. The effect of probiotics on functional constipation in adults: a systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. 2014;100(4):1075-1084. doi:10.3945/ajcn.114.089151
About the Vita Globe Editorial Team
The Vita Globe Editorial Team researches and writes our wellness content, working from peer-reviewed research, systematic reviews and guidance from bodies such as the NIH and the FDA. We cite our sources inline and update articles when the evidence changes.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for informational purposes only and is not a substitute for medical advice. Talk to your healthcare provider before starting any new supplement, particularly if you are pregnant, nursing, taking medication, or caring for a child.
