Tips for Preventing Running-Related Stomach Issues

An elite runner shares insider advice for avoiding tummy troubles related to long distance running


Many runners are all too familiar with the digestive issues that commonly arise when training for or racing long-distances.

And if you’re not yet familiar with this running-related dilemma, well then you can use the following tips to avoid it and, if you’re lucky, give thanks for the fact that you were proactive enough to never have to deal with such an unpleasant experience.

According to Competitor Running, the most common cause of GI distress and digestive issues for runners is dehydration.

“Dehydration during taxing long runs and hard workouts leads to a lot of the excruciating stomach problems runners experience both during, and immediately following, their runs,” wrote Caitlin Chock. “When running, the body’s main focus becomes supplying the muscles and lungs with oxygenated blood. In doing so, blood is diverted away from the stomach and intestines as the fatiguing runner’s body puts digestion on the back-burner.”

Needless to say, this can lead to a great deal of discomfort and even interrupt your workouts or a race. In fact, Active reported that expert marathoner Bill Rodgers once said, "More marathons are won or lost in the porta-toilets than at the dinner table."

Below, Tina Muir, a 2:45 marathoner, third place 10k finisher at the 2012 Great Britain Olympic Trials and an expert coach at RunnersConnect, offers insider advice about how runners can avoid digestive issues while training and racing over long distances.

What should runners eat before a long training run or long-distance race?
Muir says: Unfortunately there isn’t one magic food that everyone will be able to digest and feel great running from, but most important is to keep foods bland. We are told we should eat the rainbow, but before a long run, you want to make your food as white as possible, as whiter foods tend to be simple and therefore easier to digest. I recommend oatmeal, plain/dry cereal, bananas, animal crackers, and rice. Some people also like to add some peanut butter to these to help slow digestion, but that is something you will have to practice with to see if your stomach can handle it. My go-to meal is 1/2 cup oatmeal with 1/2 cup milk and 1/2 cup water, and a large banana. 

How long before a run or race should runners eat?
Muir says: Again, this is down to personal preference, but most people eat three to four hours before they run to allow their stomach to digest the food and start using it for energy, but so they are not starving. It’s also good to have another smaller snack around an hour before; this could be a banana or a plain granola bar/Powerbar. If you are running early in the morning, I would definitely recommend getting up at least an hour before to give your body time to wake up and digest the food you give it, but maybe just take in a little less than you would if you were eating three to four hours before.

What should runners fuel with during a long run or race?
Muir says: I am the queen of experimenting, and I have been practicing this a lot during my past three marathon segments. Some people like to take their fuel in liquid form, which could be a source such as Generation UCAN, Gatorade, or whatever they offer on the course of the race. Others like to use gels or energy chews and take them with water. In my previous two marathons I used liquid sources, and found a lot of success with Generation UCAN, but this means you have to either carry it with you, or be an elite runner (which I was thankful to have my own water bottles at Chicago).

Based on that, I would recommend the gel option for most people as it means they can carry them in pockets (or in your sports bra) and take them with water stations of your choice. For my upcoming London marathon, I intend on taking three Powerbar gels at miles 8, 15, and 21, and water every three to four miles. 

The most important thing about fueling for a marathon is to make sure that you practice. You want to make sure your body is used to processing fuel while running and you want to make sure it does not upset your stomach. If you practice taking those fuels during your long runs and workouts, your body will know what is coming on race day. This is also when you’ll figure out which products you (and your stomach) like and don’t like. Some of the gels were a little too thick for me, which made it difficult for me to swallow, whereas the Powerbar gel goes down much easier. That is something I would never have known without experimenting with it.

And what about hydrating?
Muir says: Once again, it is important to practice. If you know they are going to have cups of water at your upcoming race, get a loved one to stand on your long run route and hold out cups for you to practice taking and drinking. I have found that I have improved my efficiency of taking in water while moving as I have practiced, whereas at first I was choking on the water every time. You want to try to make sure you drink four to 10 ounces of liquid every three to four miles to make sure you stay hydrated, and make sure you always take your fuel with water too.

Is there anything else runners should take into account when aiming to prevent running-related stomach troubles?
Muir says: I find that on race day my stomach can sometimes be upset anyway and drinking a hot tea three to four hours before the race gets my digestion going, so I feel better by the time I get to the race. If you have practiced throughout your training cycle, your body should know what is coming, but I would definitely make sure you get up three to four hours before the race to allow your body time to wake up. I also sometimes find Tums help my stomach calm down on the morning of the race. 

Check out more training advice from Tina Muir on her blog, where she’ll be detailing her nutritional strategy for her upcoming race at the London Marathon. And for more marathon running nutrition tips, check out the RunnersConnect Marathon Nutrition Blueprint.


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