Travel can be amazing and fulfilling — but it can also wreak havoc on your digestive rhythms. If you find that your regular bathroom schedule is disrupted by your holiday plans, whether you've taken a road trip or flown across the world, you're not alone. If you can't poop when you're traveling, the food at your new holiday destination may very well not be to blame. Gastroenterologist Dr. Lawrence Brandt, professor of medicine and surgery at the Albert Einstein College of Medicine, tells Bustle that there are several reasons behind digestive issues when you travel — and while some are psychological, others are based in physics.
Part of the problem, Dr. Brandt explains, has to do with familiarity and comfort. "When people are forced to move their bowels in a foreign location which is not their usual area, they often don't feel comfortable with it," he explains. This is a problem that occurs whether you take planes, trains or cars to your destination. If you can't seem to be regular in a new destination, you may be experiencing psychological discomfort that's directly related to unfamiliar places and situations.
However, other aspects of travel will mess up your bowels regardless of your psychological attitude. A lot of travel means sitting and waiting, whether it's in a lounge, a train station or when you're in transit. "When you sit for a long period of time, or you're immobile, your intestinal motility decreases, which means the gas that's in your bowels is kept in your bowels," Dr. Brandt tells Bustle. Intestinal motility refers to the gut's ability to move things through using muscles. If you feel gassy and constipated after a long period sitting down on a plane or train, this is why — and it's a good reason for moving around regularly when you're traveling, because that will shift the gas around and out of the body.
However, there are a few aspects of air travel in particular that mean it can cause issues for digestion. One is related to physics. "As one ascends in an airplane, the pressure on the bowel increases, because of a law of physics called Boyle's law," Dr. Brandt says. If you remember your high school science lessons, Boyle's law dictates that if you observe a vessel filled with gas — like a balloon, or the human gut — in a constant temperature as the pressure around it decreases, the balloon expands, and vice versa.
"When you're sitting on an airplane and the altitude gets higher, the surrounding pressure decreases and the gas in your bowel expands," explains Dr. Brandt. The World Health Organization notes that air cabins are pressurized to replicate the air pressure at about 6,000 feet above sea level. When you're climbing so high in the air — commercial planes usually fly above 31,000 feet — the altitude is going to make the gas in your body expand, which will cause your bowels to distend. If you've ever wondered why you pass wind so often on a flight, that's why — and Dr. Brandt says it's actually a recognized medical phenomenon, called high-altitude flatus expulsion. (This is also why planes smell so terrible after a long flight.)
Another cause of in-flight gas is carbonated soda, which contains CO2. "As soon as those gases get into the warm stomach, the CO2 causing the carbonation is released, and that distends the stomach," explains Dr. Brandt. "CO2 expands at high altitudes." He also notes that chewing gum, while it's commonly used to help ears pop during take-off and landing, can cause gas issues. "When you chew gum and swallow a lot, you're also putting gas in your bowel," he says; whenever you swallow air, it makes its way into the gut, and in planes that means trapped gas. When they're all added together, these gas-inducing elements mean that your digestion and bowels will likely be thoroughly impacted by air travel, particularly if you're in the air for a long period.
If you experience a lot of trouble with digestion and bowel issues after you travel, there are potential ways to make things easier. Dr. Brandt recommends that people who experience serious gaseousness might want to take simethicone, a drug that breaks up gas bubbles in the gut, before they travel, and that they stick to a low-FODMAP diet in the days before they leave. High-FODMAP foods have a lot of sugars and sugar alcohols that the body converts to gas, and tend to aggravate issues like irritable bowel syndrome. Keeping away from them before you fly or travel might reduce problems with your bowels when you land — as long as you can feel comfortable in your new, unfamiliar toilet, that is.