Why does travel mess up your gut? Does flying make you bloated? Are some people just more prone to disruption—and does jet lag have anything to do with it? Inquiring minds want to know. We asked Harvard gastroenterologist Dr. Trisha Pasricha to explain what goes on at the gut level when we’re on the road, what actually works (and doesn’t) for preventing an explosive situation, and what she always packs to keep things moving.
Can you tell us a bit about you and your background?
I’m a gastroenterologist and researcher at Harvard Medical School and Beth Israel Deaconess Medical Center, where I direct the Institute for Gut-Brain Research. My work focuses on the connection between the gut and the brain, which I find endlessly fascinating and more than slightly humbling.
I also write the “Ask a Doctor” column for The Washington Post, which means I spend a lot of time translating complex science into something that doesn’t require a medical degree to understand. My first book, You’ve Been Pooping All Wrong, came out last April—which I realize sounds like a provocation, but I promise it’s a warm one.
I run an NIH-funded laboratory studying how GI symptoms can precede neurological conditions like Parkinson’s disease. But I also have a soft spot for the more immediately practical questions—like why your colon falls apart the moment you board a plane or why you feel butterflies in your stomach on a date.
The term “gut health” gets thrown around so much—can you explain what it actually means and why it’s so important?
“Gut health” has become one of those phrases that means everything and therefore risks meaning nothing. It shows up on kombucha labels and wellness retreats with equal enthusiasm, which has made a lot of people reasonably skeptical.
What it actually refers to is the health of your gastrointestinal tract—from the moment food enters your mouth to its, shall we say, final farewell—along with the trillions of microbes that live there, and how that entire system communicates with your brain, immune system, and hormones. What many people don’t realize is that your gut has its own nervous system (the enteric nervous system), and dysfunction in this system, like from inflammation or a disruption of your microbiome, doesn’t stay local. Your gut is implicated in everything from mood disorders to immune function to, increasingly, neurodegenerative disease. So we need to stop thinking of our bowels as a passive plumbing system. It’s a brain—and that has huge implications for our overall health.
Are there any wellness trends for gut health that are overhyped or counterproductive?
Where to begin. The gut health wellness space has the unique distinction of being simultaneously under-researched and over-monetized, which is quite a feat.
Probiotic supplements are probably the most dramatic example of hype outpacing evidence. The science on which strains do what, for whom, and in what amounts is genuinely incomplete. Most supplements contain strains that have been studied in specific clinical contexts—they’re not general-purpose gut tune-ups, and for some people with certain conditions, they can actually cause problems. A container of Greek yogurt with live cultures will do more for most healthy people.
Gut cleanses and detoxes also deserve a particular mention. Your liver and kidneys are the detox department—they work continuously, without needing a three-day juice fast to function. What a cleanse often does is simply restrict fiber, which is the opposite of what your gut bacteria want. Yes, you may feel better after doing a juice cleanse for a few days—but that’s probably because you’re better hydrated and eating fewer ultra-processed foods. But you still—and always will—need more fiber.
Why do 40% of travelers deal with constipation when they travel? Are some people just more prone to digestive disruption while traveling, or is it something everyone can train their body to handle better?
Your gut is, at heart, a creature of habit—and travel is a systematic assault on every habit it has held so dearly. The 40% figure reflects how genuinely sensitive this system is to disruption.
Some people are more prone than others, yes. Those who already have irritable bowel syndrome, constipation, or anxiety tend to feel travel-related GI effects more acutely. But even people with iron constitutions will notice changes when traveling.
How much of gut issues while traveling is actually about routine disruption versus other factors?
Routine disruption is a dominant factor for most travelers—but especially if you are switching time zones, disruption to your circadian rhythm takes a big toll on your colon. Your bowel movements are regulated by your circadian rhythm, which is why most people have a fairly predictable window each day. Change the time zone, scramble the sleep schedule, eat at irregular intervals, and the whole choreography falls apart.
That said, the changes in routine are a big and real problem. Diet changes (less fiber, more processed food, alcohol), dehydration, reduced physical activity, and the psychological stress of travel all pile on.
Is there anything about air travel itself—altitude, cabin pressure, dry air—that directly affects digestion?
Absolutely, and it’s one of my favorite things to explain, because people assume they’re imagining it.
You are not alone: everyone is gassier and more bloated on an airplane.
Cabin pressure in commercial aircraft is typically set to the equivalent of about 6,000–8,000 feet of altitude. According to the ideal gas law, pressure and volume are inversely related—so when pressure drops during flight, the gas in your intestines has to expand. This is why bloating on planes is real and not a matter of personal weakness (so remember, be forgiving of your fellow passengers too). The gas has to go somewhere—and usually, that somewhere is outward.
Then there’s the dry air—cabin humidity is typically around 10–15%, compared to roughly 40–60% in most homes—which, alongside those exceedingly tiny cups the airline gives you for a drink every few hours, contributes to dehydration. When your bowels don’t get enough water, things stall.
Now, combine those factors with sitting still for hours (physical movement helps motility), eating whatever the airline has decided constitutes a meal, and the low-grade stress of air travel, and you have a fairly complete recipe for digestive misery.
Should people take something preemptively before a trip, or wait until there’s a problem?
I always like to be pro-active. Hope is not a strategy. Bring a fiber supplement anticipating the likelihood of getting backed up, and on the flip side, if you’re traveling somewhere with a high risk of traveler’s diarrhea, there are evidence-based options worth discussing with your physician before you go—Pepto Bismol, taken 4 times a day, can reduce the risk of traveler’s diarrhea by around 65 percent.
How do jet lag and circadian disruption affect the gut and overall health? Do you have any general strategies for dealing with jet lag?
Jet lag is a whole-body problem, not just a sleep problem. Your gastrointestinal tract has its own circadian rhythm—it’s anticipating meals, regulating motility, and calibrating secretions based on the time of day. When your internal clock gets out of sync with local time, the gut gets confused.
For jet lag generally: light exposure is your most powerful tool. Get outside in natural light in the morning at your destination—it’s the primary signal that resets your circadian clock. Adjusting meal timing to local time as quickly as possible (eating lunch at lunch time even if your body thinks it’s 2 am) also helps accelerate adaptation.
What’s the deal with not being able to poop anywhere but home? Is that psychological or physical?
Both, and the fact that it’s partly psychological doesn’t make it any less real—which is something I say often. As many as 3 out of 4 people struggle to poop in public bathrooms.
Your nervous system plays a significant role in bowel function: the gut-brain axis runs in both directions. When you’re in an unfamiliar environment—or have multiple friends or cousins sharing your same hotel bathroom—your threat-detection system becomes mildly activated. This can inhibit the parasympathetic state your body needs to comfortably evacuate those sphincters. You need to feel safe to poop. That’s just the reality of it.
On the physical side, you also have all the factors we’ve discussed—routine disruption, dehydration, diet changes—converging to slow motility. Home is where your body has trained itself to go, quite literally. Some people find that replicating small elements of their home routine (same time, same reading material, same general posture of existential contemplation) helps their nervous system relax enough to cooperate.
What actually causes traveler’s diarrhea—and how do travelers avoid it without being paranoid about everything they eat?
Traveler’s diarrhea is caused primarily by ingesting food or water contaminated with bacteria, viruses, or far less commonly parasites. The risk varies significantly by destination—Sub-Saharan Africa, South and Southeast Asia, and parts of Latin America carry higher risk than, say, Western Europe or Japan.
The classic advice—”boil it, cook it, peel it, or forget it”—remains basically sound for high-risk destinations, but I understand that obsessively avoiding all street food in Bangkok is both joyless and probably unnecessary. Personally, I love trying street food and dive restaurants when traveling, but I avoid adding sauces or condiments that have been sitting at room temperature. Cooked food that’s served hot is generally safe. Fruits and vegetables you can peel yourself are fine. The highest-risk items tend to be raw vegetables washed in local water, ice of unknown origin (remember that when you order a cocktail on the rocks), and anything that’s been sitting out. Street food cooked fresh in front of you is often safer than a buffet that’s been warming for hours.
Also: wash your hands. Constantly. This is boring advice, but it is responsible for preventing more illness than any supplement.
Suppose you’re on a once in a lifetime trip and avoiding traveler’s diarrhea is a top priority. My advice then would be to take Pepto Bismol four times a day (two tablets every 3-4 hours while awake with no more than 8 tablets in a 24 hour period). Always run this by your own physician who knows your own history (people with kidney disease or who are taking aspirin should avoid Pepto Bismol), but randomized controlled trials have shown this can reduce your risk of traveler’s diarrhea by around 65 percent. Yeah, it’s a bit annoying to take a pill that frequently (and yes, it needs to be dosed 4 times a day or it’s ineffective)—but for some dream vacations, that could be a solid insurance policy.
Is it true that traveler’s diarrhea can have permanent impacts on your gut?
Yes, in a subset of cases. Most episodes of traveler’s diarrhea resolve within a few days, and then the person goes home, recounts the story at dinner parties, and suffers no lasting effects.
But a meaningful percentage of people, somewhere between 10-25%, will go on to develop irritable bowel syndrome. The acute infection triggers inflammatory changes in the gut that, in some individuals, persist long after the pathogen is gone.
This is a real and recognized phenomenon, and if weeks after you’ve come home from your trip and still have unexplained IBS symptoms like cramping, bloating, pain, and changes in how often you go that started after a GI infection, it’s worth discussing with a gastroenterologist. There are effective treatments.
Should people pack antibiotics just in case?
This is a nuanced one, and the answer has shifted somewhat as antibiotic resistance has become a more pressing concern.
The traditional approach was “carry a course of antibiotics and self-treat if things get bad.” The problem is that many of the bacteria causing traveler’s diarrhea in high-risk regions have become resistant to the antibiotics that were previously first-line treatments. Using antibiotics unnecessarily also disrupts your microbiome in ways that can, ironically, increase your vulnerability to further GI problems.
The current thinking is more selective: antibiotics are appropriate for severe cases—fever, bloody stool, symptoms that aren’t improving—in which case, you should visit a local physician anyway. For moderate diarrhea without those red flags, oral rehydration and time are often sufficient.
If you’re traveling to a high-risk destination for an extended period, or if you have an underlying health condition, it’s worth having a conversation with your doctor beforehand about whether carrying something makes sense for your specific situation. And certainly, I don’t recommend taking antibiotics as a protective measure before there is any actual illness.
What about charcoal pills—do they actually work?
The evidence for using it to prevent or treat traveler’s diarrhea is quite weak and there’s also an underappreciated downside: activated charcoal is indiscriminate. It will bind to medications you’re taking and reduce their absorption, which is a problem if any of those medications are important.
Is it okay to take Imodium, or does that just trap something inside one’s system?
Imodium (loperamide) is generally safe and appropriate for the right circumstances—it slows gut motility and reduces the frequency and urgency of diarrhea, which is genuinely useful when you have a seven-hour flight and things are going badly.
The “trapping it inside” concern is actually mostly unfounded in healthy adults. Your immune system deals with the pathogen regardless—the Imodium just reduces how dramatically your gut announces it.
However, don’t take loperamide if you have fever, bloody stool, or severe symptoms. In those cases, the diarrhea may be your body actively trying to expel something serious, and slowing it down can be counterproductive.
What are some things everyone should keep in their travel pharmacy kit?
- Oral rehydration salts—the most underrated item on this list. Not sports drinks (the electrolyte ratio is different, plus carrying liquids is hard); actual oral rehydration salts that you can mix into a bottle of water. Pharmacies in most countries carry them.
- Loperamide (Immodium)
- Fiber supplement (I like psyllium husk)
- Pepto Bismol
- Your usual medications—pack twice as much as you think you’ll need, and split them between your checked and carry-on luggage.
- Hand sanitizer for situations where soap and water aren’t available, though it is not a substitute for handwashing.
What do you personally do to preserve your gut health on vacation?
I start behaving like I’m already in the time zone of my destination the moment I get on the plane. I bring a really cozy travel blanket and wide eye mask to block out all light so I can shift my body as easily as possible. I also try to maintain parts of my usual morning routine to kickstart my colon on vacation—I drink coffee early and take a short walk even if I’m not in the mood for a full workout. These things help keep my system on track.
This is perhaps the most important part: I aggressively seek out extra fiber on vacation. At very least, I take a fiber supplement with me because constipation is the last thing I want to deal with. Side salads don’t cut it—I eat real fruits and vegetables on vacation like kiwis and peas whenever I can.
How do you approach staying healthy and relaxed when you travel by plane? Do you have a typical travel-day wellness routine?
I bring along an empty reusable water bottle with me through security so I can fill it up as much and as often as I want once I’m in. Otherwise, you’re relying on the flight attendants making rounds with a tiny cup every few hours. This has really helped ensure I don’t land dehydrated.
I also try to eat a real meal with protein and fiber before boarding rather than relying on what’s available in the air. And I always have snacks. Nuts make a great travel snack and they’re bursting with fiber.
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