Friday, June 6, 2014

Gastrointestinal Issues in Runners and Strategies to Overcome Them

Bill Rogers, a famous American runner that won four times the Boston and NYC marathon's between 1975-1980 and a 2000 USA Track & Field Hall of Famer stated, "more marathons are won or lost in the portable toilets than at the dinner table". Obviously, he was well aware of the gastrointestinal (GI) issues runners face.
GI issues have a variety of symptoms including: diarrhea, nausea, vomiting, bloating, belching, cramps heartburn and bloody stools. Symptoms are more common in women, younger athletes, elite athletes and people with a history of GI issues. It is estimated to occur in 30-90% of distance runners during and/or after exercise. Complaints of GI issues differ in severity and they may cause a decline in performance and recovery.


There are three main reasons for GI problems:

  • Physiological - When we exercise, depending on the intensity, blood supply to the gut may decrease by up to 80% in order to transfer more blood to the working muscles, skin and heart. This in turn may cause diarrhea, nausea, vomiting and stomach pain.
  • Mechanical -   Running is a high impact sport with continuous pounding. This pounding also influences the GI tract which in turn can cause GI symptoms. Therefore, runners have a tendency to have more problems than bikers. 
  • Nutritional - The meal timing before exercise as well as beverage and food choices may cause GI symptoms. A meal shortly before running, rich with fiber, fat and protein will cause GI symptoms because these nutrients have a slow emptying rate in the stomach. Drinking a concentrated carbohydrate beverage during or slightly before a race will cause GI symptoms. Moreover, dehydration intensifies GI symptoms. As discussed in the previous blog on alcohol and performance, drinking the night before a run several drinks can cause GI symptoms probably due to its diuretic effect. 
  • Note; Certain people may have a medical condition such as: celiac disease, lactose/fructose mal-absorption and irritable bowel syndrome to name a few, that makes them more susceptible to GI symptoms

Since this blog is a nutrition blog, lets talk about some nutrition strategies to prevent GI symptoms:

  • Hydration, hydration, hydration - before a run, make sure you are hydrated. Focus on hydrating well throughout the day. 
  • Avoid beverages during or slightly before a run rich with fructose such as juice. Prefer water or if running long distance, a sports beverage with 6-8% carbohydrates such as Gatorade or Powerade.
  • Avoid high fiber foods 1-2 hours pre-exercise as well as the day before a big race. 
  • Avoid high fat and high protein foods 1-2 hours pre-exercise
  • "Train the gut" - the gut is very adaptable, therefore, train your gut by eating during your training as well as before (if activity is lower than 60-90 minutes there is no need to eat anything during and water should suffice). Experiment with foods before a training session to check what works and what doesn't.
  • Avoid using non-selective, non steroidal anti-inflammatory drugs (NSAIDs) such as Aspirin and Ibuprofen as they tend to increase GI symptoms.
  • Avoid lactose containing milk products if you think or know that you are lactose intolerant. 
  • Avoid or limit alcohol drinking before a morning run or a big race
It is very important that if you have severe GI symptoms such as bloody stools, you consult with a medical professional.
For specific guidance and assistance if you suffer from the symptoms noted above, consider consulting with a sports dietitian to help you with strategies to prevent any GI symptoms.


  1. I attended the NSIC Athletic Trainer workshop in Sioux Falls last week where you spoke. You recommended that we have our athletes tested for vitamin D. What is the best way to do this?

  2. The best way is to get a blood test of 25(OH)D, which can be ordered by your physician and could potentially be covered by your insurance.
    You can also get it yourself. The Vitamin D council explains it nicely as noted in the link below:
    Thanks for reading!


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