6 tips to avoiding tummy trouble when you run

September 04, 2015                 4m read time
Kathy Murdock

So you’re ready to make the jump from 10Ks to half marathons. You know you’re going to spend a lot more time thinking about things like tempo runs and carb-to-protein ratios. Unfortunately, you might also find yourself talking way too much about your, and your running friends’, BMs. And no, we aren’t talking body mass. Tummy troubles are a big problem for many endurance runners, particularly in the beginning.

Something funky happens in your GI tract when you increase mileage, and your bowel movements can go a little wonky. (It’s gross, we know, but it’s going to happen so it’s better to be prepared.) When you run far, blood gets diverted from your stomach to your working muscles (i.e. your legs). When you stop running, that blood rushes back into your stomach. In some runners, particularly those new to distances, this causes stomach distress in the form of cramping, pain, and diarrhea (or runners’ trots). 

Since spending an hour post-race in the (usually nasty) porta potties is probably not how you envisioned your big finish, we’ve gathered together some tips for easing stomach distress. Test these out during training to find what works best for you.   

Runners wait in a line for a single porta potty. Rob MacEwen

Runners wait in a line for a single porta potty.

Rob MacEwen


1. Eat more protein and less carbs the night before a long run

Yes, this sounds contradictory to “carbo loading,” which runners have been told for years is the way to eat before a race. While this ritual isn’t a no-no for every runner, it can wreak havoc on some runners’ stomachs. Play around with your pre-long run dinner menu. Add more protein and cut back on carbs. Some ideas: a hamburger or turkey or veggie burger with baked sweet potato wedges and another vegetable, or a piece of salmon with a side of rice and a veggie. Eat your veggies, but watch out for those that might upset your stomach, such as a large green salad. And avoid fried foods. The high fat content can speed up stomach elimination and cause diarrhea on race morning.  

2. Skip coffee the morning of the run

As you may already know, coffee has a tendency to “get things moving” in the morning due to its ability to cause stomach contractions. But when you have more than ten miles to run, you don’t want them moving too much. If you drink a cup of java on long run days, skip it one week to see if this helps. Substitute hot tea if you want the feel of a warm beverage without the possible stomach upset. And if you can’t forgo that cup of joe, drink it at least one hour before you run.    

Runner refuels with trail mix. ZOZI Journal

Runner refuels with trail mix.

ZOZI Journal


3. Eat real food instead of sugary sports drinks during the race

Some runners do fine consuming sugary sports drinks on the run; others find these energy drinks upset their stomachs. The belly blowouts could be due to stomach muscles shutting down as the blood gets pumped to working muscles (as mentioned above). They could also be caused by the high sugar content. (If you do consume gel on the run, always do so with some water to dilute the high sugar content.) Real food might fix stomach upset associated with gels. To eat on the run, consider foods that are easy to carry, eat while in motion, and store. The following are some solid options:

  • Peanut butter and honey sandwiches, which are easy to carry and provide a good mix of carbs and protein
  • Graham crackers, because they offer a sweet fix on the run (make a graham cracker and nut butter sandwich to add in some protein)
  • Fig cookies, used by many endurance athletes, are sweet and easy to carry
  • Trail mix, mixed by you with your favorite carb and protein treats like M&Ms, peanuts, and pieces of cracker

Make food the night before the race and store it in plastic baggies. (They’re generally the easiest containers to open, close, and eat from on the go.) Test how often you need fuel during your training runs. For instance, try eating a small amount at miles 5, 8, and 10. If this is too much, try eating at miles 6 and 10.

4. Try low-sugar electrolyte replacement drinks or tablets

If sugar bothers your stomach on race day, test out electrolyte replacement drinks and tablets, such as nuun, during training. If you find one that works, you must carry it with you on race day unless it is the same drink being served at water stations. Use a hydration pack or waist belt, but do so during practice runs to get used to the added weight.   

Marathon runner grabs a cup of water to stay hydrated and keep moving. ZOZI Journal

Marathon runner grabs a cup of water to stay hydrated and keep moving.

ZOZI Journal


5. When should you be concerned?

While stomach problems are very common in endurance runners, you should be concerned if there is blood in your stool, you spend large amounts of time in the bathroom after each long run, or you experience symptoms such as dizziness, racing heart, headaches, or vomiting along with the diarrhea. In these instances, see a doctor stat to rule out other problems.

6. Get to the bottom of the matter

If you’re lucky, the added miles won’t cause GI problems. But if they do, become a detective during early training runs to determine the causes—and fixes—of your stomach distress. Test the tips to find what works best for you. You might need to make one adjustment; you might need to make several. Once you find the cure, follow through on race day so you can spend time at the post-race party instead of on the porcelain throne.

Kathy Murdock

Kathy works as a freelance writer and marketer from her home in sunny Florida. An avid runner, she has completed nine half marathons and two full marathons, along with a variety of other racing distances. She loves her family, long runs, hot coffee, and peanut butter.

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