4 Things Gastroenterologists Want Runners to Know

Lauren Bedosky
by Lauren Bedosky
Share it:
4 Things Gastroenterologists Want Runners to Know

From cramps to nausea to diarrhea, running and digestive troubles often go hand-in-hand. For many runners, digestive troubles appear at the worst possible moment: In the middle of a run or race. In fact, one survey found that, over the course of 30 days, male runners experienced at least one gastrointestinal (GI) issue during 84% of their runs. For female runners, that number was roughly 78%.

To help you avoid future mid-run disasters, we tapped a GI doctor for the lowdown on running and GI health.



Your GI tract — made up of the mouth, esophagus, stomach, small intestine, large intestine and anus — plays a major role in your overall health. “The GI system is sometimes referred to as another ‘brain,’ as it is so intimately involved with other systems of the body,” says Dr. Peyton Berookim, a board-certified gastroenterologist in Beverly Hills, California.

In fact, the microorganisms in your gut (known as the gut microbiota) are thought to communicate with your brain, and your brain with your gut, according to a 2012 review. This concept is known as the microbiota-gut-brain axis, and suggests the health of the gut affects how the rest of the body functions, and vice versa.

Exercise, in general, is an effective way to improve GI health. According to a 2017 review in Oxidative Medicine and Cellular Longevity, exercise may increase the number of healthy bacteria in your gut, as well as diversify your gut microbiota as a whole — all key for staying healthy.

However, runners have to tune-in to GI health, as a healthy digestive system only makes workouts more satisfying. Mostly, this means knowing what and when to eat before a run, as this impacts how you feel both during and after, Berookim says.



A pre-run snack (or even a meal) can boost blood sugar levels and top off your stores of muscle glycogen (a quick-acting carb source), providing you with more fuel for longer, harder runs, according to the Academy of Nutrition and Dietetics.

That said, it’s important not to eat right before your run, as this may lead to gut-related issues, such as heartburn, diarrhea and gas. “When one runs, their body experiences the physical jostling of organs, including the colon, and contents within will make their way down the digestive tract and out,” Berookim says.

What’s more, running encourages your body to direct blood toward your working muscles and tissues, “but if one has just consumed a large meal, the body will want to direct that blood to the stomach and digestive system for breakdown of that food,” Berookim says. The result is often nausea and sometimes even vomiting.

If you need a pre-run snack, choose something small with a bit of carbs and protein — like a banana with a tablespoon of peanut butter — and wait 30–60 minutes before heading out. A bigger snack or meal will likely need more time to digest (Think: 2 hours), especially if it contains fat or fiber. However, pre-run meal timing is fairly individual, so experiment to find what works for you.



Hopefully, you already know how important it is to stay hydrated — especially if you’re going for a run. Drinking plenty of water is not only key for staying energized and cool during exercise, but it’s also a great strategy for keeping GI issues at bay.

In one study, researchers had a group of active men sit in a sauna until they had lost roughly 3 percent of their body mass in sweat. Then, the men cycled for 90 minutes at 70% of maximum intensity. Researchers found that exercising while dehydrated caused foods and liquids to sit in the stomach longer, leading to greater nausea during exercise, compared to exercising while well-hydrated.

So, be sure to drink plenty of water before your run to keep your gut — and body — healthy.

Hydration needs vary from one person to the next, but the American College of Sports Medicine recommends drinking at least 16–20 ounces of water 4 hours before exercise and drinking when thirsty during exercise.



While staying hydrated before and during your run can help prevent or ease gut issues, take care when choosing your beverage. “It is important to stay hydrated before your run, but stay away from diuretics and laxatives that will make you have to stop and go,” Berookim says.

For example, while pre-run coffee and other caffeinated drinks are often used to boost running endurance and performance, caffeine can also stimulate your bowels, increasing the odds you’ll need to make a mid-run pit-stop.

Caffeine is quickly absorbed through the GI tract, with elevated levels appearing in the bloodstream within 15–45 minutes, and peaking at the 60-minute mark, according to a paper from the International Society of Sports Nutrition.

If you need a jolt of caffeine before your run, try to consume it an hour before you head out, just to play it safe. However, caffeine affects everyone differently, so experiment to find what works for you.

About the Author

Lauren Bedosky
Lauren Bedosky

Lauren is a freelance fitness writer who specializes in covering running and strength training topics. She writes for a variety of national publications, including Men’s HealthRunner’s WorldSHAPE and Women’s Running. She lives in Brooklyn Park, Minnesota, with her husband and their three dogs.


Never Miss a Post!

Turn on MapMyRun desktop notifications and stay up to date on the latest running advice.


Click the 'Allow' Button Above


You're all set.

You’re taking control of your fitness and wellness journey, so take control of your data, too. Learn more about your rights and options. Or click here to opt-out of certain cookies.