What Happens to Your Gut When You Travel, According to a Gastroenterologist

Okay, wellness buffs, time for real talk. In the quest to understand our bodies, there’s a lot of chatter about brain science. What is the picture of your brain with anxiety? What happens to your brain when you exercise? What happens to your brain when you fall in love? Well kudos to you, grey matter, for hogging the spotlight, but what I want to get into is something more core to my being, and I daresay more useful in a busy life of weekends away and seasonal travel. Namely, what happens to your gut when you travel, and why does everything from constipation to traveler’s diarrhea have the potential to wreck an otherwise balanced biochemistry, causing stomachache, headache and worse? (Yep, I’m talking the aforementioned irregularity issues.) I spoke with a noted gastroenterologist for an explainer on everything from microbiomes to probiotics, as well a useful tips about feeling great on long plane trips, at altitude and in places where, maybe don’t drink the water.

Dr. Will Bulsiewicz is an award-winning gastroenterologist, two-time New York Times bestselling author (Fiber Fueled and The Fiber Fueled Cookbook), and U.S. medical director for ZOE, a company combining world-leading science with at-home testing to help clients make the smartest food choices for their bodies. Bulsiewicz (known as Dr. B.) is the creator of the Plant Fed Gut, a seven-week masterclass in which clients heal their gut, optimize their microbiome and reverse pathogenic growth in the gut.

“It’s wild to think there is something so powerful that effects our digestion, metabolism,  immune system, hormones, mood and brain function, and it’s not even a part of our body nor is it even human.”

Dr. Will Bulsiewicz 

Basically when people refer to “gut health,” they’re talking about anything that’s a part of our system of eating and pooping. “Our gut biome is fascinating to me as a medical doctor because it really is the command center of our day-to-day health,” says Dr. B. “It’s wild to think there is something so powerful that effects our digestion, metabolism,  immune system, hormones, mood and brain function, and it’s not even a part of our body nor is it even human.” Uh, what? Dr. B explains that the gut biome is technically both inside and external to our body, since it comprises approximately 39 trillion bacteria that reside on the external of our whole body as well as our digestive tract. “So they’re in your eyes, nose, mouth, a women’s vagina, but they are most concentrated in our colon, which is our large intestine. And technically what’s inside our colon is actually outside your body.” Here’s how Dr. B explains this weird perspective: You put something (let’s say food) in your mouth and swallow it, so it’s as though that food is entering into a tube and that tube is never broken. “Basically, it started outside your body and it remains outside your body as it passes through,” he says.

Well, everyone’s microbiome is unique to them—"even a pair of identical twins raised in the same household will only share 35 percent of the same microbes, and it’s thought to be more unique to a person than fingerprints,” Dr. B. says. So, while every body is going to react differently to the stresses of travel, there are some common reactions. At high altitudes, the lack of oxygen depletes our body of that life-giving element, and a recent study suggests this oxygen deficit increases pathogenic biomes (i.e. “bad bacteria”). Also, shifts in the cabin pressure are changes in the altitude which can cause gas bubbles, say from drinking a carbonated beverage, making people feel bloated. “The number-one medical issue on flights are digestive issues because the shifts in gas can make you feel unwell. You’re sitting in a hunched over tight space, you’re not getting up and walking around and if you fart, you’re basically insulting the people seated next to you, so you’re trying to hold it back which makes is worse,” Dr. B. says.

 “In a perfect world you have a bowel movement the morning before the flight so you’re not constipated on the plane,” Dr. B. says. “If you’re prone to constipation, just bring your own non-carbonated drinks or water. And bring a handful of almonds packed in your carryon bag, since by contrast a high-fiber snack might make your issues worse. Even crudite with hummus—beans—is going to be fermented by your gut. It's good for you on the ground but more prone to inducing gas in flight.” And avoid the salty snacks that cause bloating.

“The concern is traveler’s diarrhea, which can be brought on by exposure to microbes that we are not used to,” Dr. B. says. “In these places, the local people are used to them, but we’re not exposed, so we are not used to them. It’s likely the water is not treated the same way in other places as we treat our water in the United States. Like E. coli…every ounce of water has a percentage of the bacteria, if you ingest enough of it, it crosses a line and gives you traveler’s diarrhea.” One of the purposes of our gut microbiome is to protect us from this bacteria. For example, when we take antibiotics, we can be prone to new infections developing, for example a bacteria called C. diff grows because we have suppressed the good bacteria that usually keeps it in check.

So, follow the travel food safety advice of the CDC: “Avoid eating raw meat or seafood, including items “cooked” with citrus juice, vinegar, or other acidic liquid (such as ceviche).” That’s because all these ingredients have not been basically sterilized by fire, ie cooked. (That’s a lesson I won’t soon forget after losing 5 pounds in two days after eating a large plate of steak tartare at an outdoor café in the south of France.)

Want to be proactive? Take a probiotic before you leave for your destination, advises Dr. B. He recommends taking Saccharomyces boulardii to protect your healthy gut flora and to prevent and treat of several gastrointestinal diseases—studies show it works. “Make a plan for your gut health before you go,” he advises, suggesting increased water intake, early morning sun exposure (because circadian rhythms are tied to the microbiome). And consider a fiber supplement, just to keep yourself regular. And keep moving your body—it’s the best way to keep your digestion from quitting working while you’ve quit work on vacation.