This past weekend, I had my first DNF. For those not up to date with their runner’s lingo, this means “Did Not Finish.” I ran the Oakville half-marathon on Sunday as part of preparation of my bigger goal of the Scotiabank Waterfront Marathon. This half-marathon did not go anywhere near as planned, and I had to pull out. The only good thing that came out of this race was a topic for this week’s blog: runner’s trots. It seems fitting that all over social media this week were headlines about the “mad pooper.” She may have passed my mind several times during this race.

I frequently counsel athletes on ways of preventing the runner’s trots and other GI issues while on the run. However, I’ll be the first to admit that I’m not always the best at practicing my own advice. I think all runners at one point or another have experienced GI issues while running. I certainly have, but never in a race. Believe me, it’s something I never want to experience again, nor something I ever want another runner to experience. Please read on so you can learn from my own misery.

GI issues can be caused by so many things. Runners are at an especially high risk because of the mechanical stress of running. The up and down motion of running is physically jostling to the gut. This is why it’s not as common in other sports, like biking. Another cause is that during physical activity, blood moves away from the gut to working muscles. This lack of gut blood flow can irritate the gut and cause GI distress.

One of the common causes of the runner’s trots is eating certain “culprit” foods before a run. This includes foods high in:

  • Fibre since it speeds up movement through the gut and contributes to gas production. Such as: bran, broccoli, beans, legumes etc.
  • Fat since is slows down movement from the stomach. Such as: pastries, cream, deep fried foods, peanut butter etc.
  • Caffeine since it speeds up movement through the gut. Such as: coffee, tea, cola etc.
  • Sorbitol since it acts as a laxative. Such as: chewing gum, diet candies etc.

For instance, while a salad topped with broccoli, berries, nuts and avocado may seem like a very healthy choice, it’s probably not your best pre-race fuel. Most people tend to do better with plain foods such as bagels, banana, oatmeal etc.

I don’t think that consuming a food high in any of the above was the cause of my GI distress. I ate my typical race morning breakfast. Yes, I did consume caffeine in my coffee, but I do every morning before I run without it causing any issues. I think that my cause was dehydration. Sunday was extremely hot. Dehydration is a common cause of runner’s trots. This is because dehydration reduces our blood volume and further reduces blood flow to the gut.

I went into the race well hydrated. However, I made a rookie mistake and did not listen to the advice that I usually give my clients. I did not take any water along the course. Typically, you should be aiming to drink enough fluids during a race to prevent the greater than 2% loss in body weight. I didn’t have access to a scale pre- and post-race to see how much weight I had lost, but I’m sure that it would have been greater than the 2% body weight. Another good way to tell your hydration status is urine colour. Urine should be a light colour if you are adequately hydrated. Mine certainly was not this colour post-race.

I’m of course extremely disappointed over this race. However, I did learn a huge lesson. I am also thankful that I learned it now, rather than a more important race. Onward I go!

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Categories: Megan Kuikman

Megan Kuikman

Hello! I’m Megan Kuikman. I’m a Registered Dietitian with specialized training in sports nutrition. My goal is to help athletes and active individuals achieve a healthy attitude towards health, training, and food. I empower athletes to fuel properly for training in order to restore their health and enhance performance. You can get in touch with me at:


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