What My GI Doctor Taught Me About Running, Gut Health, and IBS Symptoms
Last month, I wrote an article titled “Exercising with IBS: How to Safely Return After a Flare-Up.”
Since then, I have been to the GI doctor and started implementing some of the guidelines he gave me. I also wanted to share some of the insight he provided about the gut-brain connection, hydration, and the gut microbiome.
Let me start by saying the irony was thick.
This GI doctor was actually one of my top referring physicians back when I worked in outpatient nutrition counseling. Becoming one of his patients felt very full-circle. I explained my symptoms, my diet history, my training schedule, and the gastrointestinal issues I had been experiencing. Honestly, I expected him to immediately place me on a strict elimination diet.
Instead, he listened.
And surprisingly, he told me not to change much yet.
Understanding Runner’s Colitis
Because I am currently training for a marathon and described symptoms occurring during endurance exercise, he felt my symptoms were most consistent with Runner’s Colitis.
Runner’s Colitis—also called ischemic colitis—is inflammation of the large intestine caused by reduced blood flow to the gastrointestinal tract. While ischemic colitis is more commonly seen in adults over age 60, it can also occur in endurance athletes, particularly long-distance runners.
Research suggests several factors may increase risk, including:
- Prolonged endurance exercise
- Dehydration
- Heat exposure
- Certain medications, such as estrogen, pseudoephedrine, migraine medications, and some cardiovascular medications
During intense exercise, blood flow is redirected away from the gastrointestinal tract toward the muscles and cardiovascular system. Combined with dehydration and physical stress, this may contribute to GI symptoms in susceptible individuals.
Symptoms That Felt Very Familiar
Of course, once I heard the diagnosis, I immediately started researching it myself.
And honestly?
I realized I had experienced many of the classic symptoms repeatedly throughout my running journey.
- Nausea
- Diarrhea
- Urgency to have a bowel movement
- Abdominal pain and cramping
- Bright red or maroon-colored blood in the stool
The blood component can be particularly alarming and understandably causes significant anxiety for many runners experiencing it for the first time. For me, the abdominal pain and cramping were especially difficult because they could either build gradually or appear very suddenly during exercise.
The Gut-Brain Connection
One of the most interesting parts of my appointment was our discussion about the gut-brain connection.
I explained that I already knew many of my trigger foods—and ironically, most of them are already Low FODMAP-friendly foods—so following a strict Low FODMAP diet would likely not provide much additional benefit for me personally right now.
(And to be clear, I still think the Low FODMAP diet can be incredibly effective for the right individuals.)
My doctor also did not want me to eliminate gluten immediately. Instead, he wanted me to wait until after my marathon before making major dietary changes.
That surprised me at first.
But his reasoning made a lot of sense. He explained that anxiety, performance pressure, and psychological stress can significantly influence gastrointestinal symptoms. Research shows that approximately 95% of the body’s serotonin is produced within the gastrointestinal tract, and serotonin signaling plays an important role in gut motility, sensation, and GI function.
Because of the strong gut-brain connection, the emotional pressure surrounding marathon training and race performance may directly influence how the GI tract responds to intense exercise.
Honestly, hearing this was validating. As athletes, we often think about muscles, endurance, hydration, and fueling—but not always the emotional stress load our bodies are carrying simultaneously.
Hydration Became a Major Focus
Another major focus of our conversation was hydration.
I train in extremely hot, humid conditions, often running in temperatures above 85°F and humidity above 90%. Dehydration is believed to play an important role in exercise-induced ischemic colitis and other GI symptoms in endurance athletes.
Since my appointment, I have become far more intentional about:
- Increasing daily fluid intake
- Using electrolyte and isotonic hydration beverages during longer runs
- Avoiding known dietary triggers
- Temporarily avoiding alcohol during marathon training
And yes…
I also bought a Squatty Potty.
Honestly, it may have been one of my better investments lately.
What Happens Next?
Once my marathon is complete and recovery is underway, I have a follow-up appointment scheduled with my GI doctor.
At that point, we will decide whether additional interventions make sense, including:
- A temporary gluten elimination trial
- Further GI testing
- Possible colonoscopy evaluation
For now, the primary goals are symptom management, optimizing hydration, and minimizing additional stress on the GI tract during training.
The Bigger Lesson
This experience has been humbling.
Even working in healthcare and understanding nutrition does not make someone immune to digestive issues or immune to occasionally ignoring what their body is trying to say.
But this process also reinforced something incredibly important:
Gut health is rarely just about food. The gut microbiome, hydration, exercise intensity, stress levels, sleep quality, nervous system regulation, and emotional health all interact in ways we are still learning to fully understand. And sometimes the best thing we can do is slow down, listen to our bodies, and ask for help when we need it.
Stay tuned—I will probably continue sharing updates along the way.
FAQs
What is Runner’s Colitis?
Runner’s Colitis, also called ischemic colitis, is inflammation of the large intestine caused by reduced blood flow to the GI tract during intense exercise.
Can running really cause GI symptoms?
Yes. Endurance exercise may contribute to nausea, diarrhea, cramping, urgency, bloating, and other GI symptoms due to reduced blood flow, dehydration, heat stress, and gut-brain interactions.
Why does stress affect the gut so much?
The gastrointestinal tract and brain are closely connected through the gut-brain axis. Stress and anxiety can affect gut motility, sensitivity, and digestive symptoms.
Can dehydration worsen GI symptoms in athletes?
Absolutely. Dehydration may reduce blood flow to the intestines and increase the risk of GI distress during prolonged endurance exercise.
- Mayo Foundation for Medical Education and Research. (2024, November 7). Ischemic colitis. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/ischemic-colitis/symptoms-causes/syc-20374001
- Moses, F. M. (2005). The effect of exercise on the gastrointestinal tract. Sports Medicine, 35(9), 713–723. https://doi.org/10.2165/00007256-200535090-00002
- Peters, H. P., Bos, M., Seebregts, L., Akkermans, L. M., van Berge Henegouwen, G. P., Bol, E., Mosterd, W. L., & de Vries, W. R. (1999). Gastrointestinal symptoms in long-distance runners, cyclists, and triathletes: prevalence, medication, and etiology. The American journal of gastroenterology, 94(6), 1570–1581. https://doi.org/10.1111/j.1572-0241.1999.01147.x
- Sikander, A., Rana, S. V., & Prasad, K. K. (2009). Role of serotonin in gastrointestinal motility and irritable bowel syndrome. Clinica chimica acta; international journal of clinical chemistry, 403(1-2), 47–55. https://doi.org/10.1016/j.cca.2009.01.028
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