Savvy Sports Nutrition:Why Running Upsets Your Stomach & How To Fix It

I’m a recreational runner. I’m not super competitive with my race times, but I like being able to complete a long race and feel good during and after. One of the reasons I started running was because I had learned about what athletes should eat for their sport, but I didn’t feel like I could fully understand sports nutrition without experiencing it firsthand. Many runners had told me they struggled with stomach issues during running. As crazy as it sounds, becoming a runner and experiencing nutrition-related issues helped me to understand and provide solutions for my clients. This week’s Savvy Sports Nutrition post is dedicated to all my runners out there.


What happens to your stomach during a run?

Let’s be real here…almost every runner has experienced cramping or the urge to use the bathroom during a run. It has happened to me (as embarrassing as it is).

To explain why this occurs, I’m going to present a common scenario. Let’s say you go out to dinner in the dead of winter. After enjoying a big meal, you leave the restaurant feeling full. For some weird reason, you feel so much colder than you did before dinner. Has this ever happened to you?

You feel colder after eating because a large amount of blood has moved from your muscles and into your stomach to digest the food. Blood is an amazing thing because it recognizes where your body has work to do, and it immediately travels to that region. What does this have to do with running? During exercise, your blood goes to the the part of the body that is doing the most work–the muscles. Because of this, the blood is diverted away from the stomach, and any food that is in the stomach sits there and isn’t quickly digested. During the constant up and down running motion, any food left in the stomach will be jostled around and cause distress. Even without food, the physical shaking of the stomach during running is enough to cause distress. Think about if I took your stomach out of your body and shook it up and down constantly for an hour. That’s pretty much what running does to your digestive system. A seasoned runner will eventually adjust to this feeling, but it will definitely cause problems for a new runner.

Lastly, exercise moves food quickly through your intestines. Unfortunately, this is just a natural occurrence, which is great for those that experience constipation but not so great for runners.

How can I avoid running stomach problems? There are several easy suggestions to avoid a wonky runner’s stomach.

Avoid high fiber foods. I once spoke to someone who was so confused because they were eating cereal (necessary carbs) before running, but she was still experiencing constant stomach problems. It turned out that she was eating high fiber cereal. The combination of high fiber foods plus running equals a guaranteed upset stomach. Avoid foods like apple juice, beans, bran, and high fiber vegetables before a run. This was really difficult for me to understand, as I usually eat a big salad with beans and cauliflower for lunch. I suggest avoiding high fiber foods the day before a race and laying low on them before a training run.

Stay properly hydrated. Dehydration can make it difficult for your intestines to absorb food, causing food to quickly travel to your bowels and creating a sense of urgency for the bathroom. This is just another reason why staying properly hydrated is so incredibly important during running.

Give your body time to acclimate. Just like your legs and lungs have to build endurance, your stomach and intestines have to acclimate to running. Going from couch to 5K will definitely lead to an upset stomach. Train your stomach to handle the up and down motion of running by gradually increasing intensity, distance and speed.

Don’t try something new on race day. Many times, runners only use gus and gels on race day. That’s a surefire way to upset your stomach. If you run for more than an hour, you should supplement your run with a sports drink, gel or gu. Try these supplements during your training runs to give your body time to adjust. These products are meant to provide fuel quickly, so they quickly digested and may cause severe indigestion.

Meet with a Registered Dietitian! Many Registered Dietitians, like myself, specialize in sports nutrition. If these techniques seem confusing or aren’t working for you, meet with a Registered Dietitian to determine the right plan for you. Nutrition is different for everyone–just because certain foods are “good” doesn’t mean they will work for you. Purchase my services here! (If you’re not in NY, we can chat via Skype or Facetime).

Choose the right foods before running: Use this handy chart for simple pre-workout meal and snack suggestions! It’s best to avoid food entirely for 1-2 hours before a race. I’m a big supporter of caffeine at least 2 hours before a race, but caffeine affects everyone differently. If coffee or tea upsets your stomach, avoid it on race day. Also, avoid high fat foods and foods containing sugar alcohols.

Questions? Have you found anything that upsets or eases your stomach while running? Tell me about it!



  • Reply
    March 5, 2016 at 11:29 am

    Great post! Keep it up:)

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