Endurance sports vs gut health
Have you ever had some abnormal bowel issues before, after, or during a run or a race? Do you feel like you can't eat certain foods during your training cycle because you are nervous about gastrointestinal (GI) distress? Did you know that between 30-90% of marathon runners experience some sort of GI distress during their event? That is a lot of people with gut stuff going on! This is common and often preventable. Today we are going to talk about how the gut responds to exercise and what we can do to limit GI issues like nausea, cramping, abdominal pain, and loose poops.
Let's talk about some science. When you start exercising you are activating two pathways, the neuro-endocrine pathway and the circulatory pathway. Both of these systems play a large role in how your GI tract responds to exercise. Part of the Neuroendocrine pathway is the sympathetic nervous system, aka your fight-or-flight" response. This essentially prepares the body to react to stressful situations by increasing heart rate, blood pressure, and alertness, while simultaneously inhibiting non-essential functions like digestion. This means that overall GI functional capacity is limited. Next comes the circulatory system. During exercise blood flow is shuttled away from the gut to provide more oxygen to the moving muscles. When there is less blood flow and oxygen to the gut there can be decreased nutrient absorption, decreased overall motility, and even cell death. Intensity and duration are important variables to remember, the longer and harder you exercise, the more at risk you are for altered GI function.
What can we do during exercise to help minimize GI distress?
Practice Practice Practice: Carbohydrate adaptation is when you get your body gets used to consuming carbohydrates. It's important to practice race day nutrition often, so that your gut knows how to use and tolerate your sports nutrition products
Keep stress low: there have been many studies that suggest that daily life stress plays a large role in running performance and GI symptoms. They found the more stressed the runner, the more diarrhea, abdominal pain, and cramping they experienced
Mixed carbohydrates: As demands increase the type of carbohydrate consumed becomes more important. Having a mix of carbohydrates like glucose and fructose can not only help performance, but can provide some relief to the stomach and small intestine.
Carbohydrates during the week: Similar to the first point, having a mix of complex carbohydrates can help repair the gut after a long/hard workout, and help replenish any lost energy stores from the liver and in the muscles.
Hydration and Electrolyte Balance: The concentration of solutions is important and should remain isotonic. This means that there is a balance of water, sugar, and sodium in the beverage to prevent osmotic shifts and promote the absorption of said fluid and electrolytes.
We learned above that there can be some damage to the gut after a long and hard workout. The term "Leaky Gut" gets thrown around a lot in the GI and endurance world, so I want to take some time to address it. Leaky Gut is a term that is often used to describe gut permeability. The gut is selectively permeable and wants to let in water, carbohydrates, nutrients, and good bacteria, all while keeping viruses and harmful bacteria out. When there is cell damage, the gut cannot fully keep out the bad guys and absorb the good stuff, so as a result, people can experience bloating after eating, cramping, and loose stools.
Here are some nutrition strategies that can help repair your gut and get it acting less permeable ie "leaky"
Increase your variety of plant-based fibers, like fruits, vegetables, and grains. Endurance athletes usually do not have good fiber intake due to the fear of having abnormal bowel patterns, but gradually increasing your soluble and insoluble fiber can help repair gut mucosa.
Polyphenols: this is the variety of colors of fruits/vegetables. Every color offers different micronutrients and anti-inflammatory properties. These are also poorly absorbed, which is a good thing because the bugs in the colon also get to feed off these foods.
Limit alcohol: I hate to be that girl, but alcohol has a direct effect on the gut mucosa. The good thing is the gut regenerates its cells every 5 days or so. So ideally, no alcohol before a long run or races, and like everything, all in moderation
Some supplements can help with gut barrier function and symptom management. Soluble fiber supplements are good for both constipation and diarrhea. Well-tolerated fibers like psyllium husk and guar gum are fantastic in regulating bowel movements. Be careful around certain prebiotic fibers like inulin, chicory root, Jerusalem artichoke, as these can contribute to gas and bloating. Can fiber improve performance? No, but it can help with the perceived level of exertion and prevent GI distress during a race. Probiotics are another common supplement that gets a lot of press. We don't have a lot of good data supporting extra supplementation of probiotics but there can be some small improvements with limited risks. When it comes to performance, similar to the fiber studies, probiotics did not improve finisher times, but athletes felt better at the end of race after supplementing with probiotics.
Key Takeaways
Endurance efforts lasting longer than 60 minutes can impair permeability of the gut
Increase duration and intensity can contribute to altered GI function like pain, cramping, and loose stools
Practicing with carbohydrates/fueling during exercise along with mixed types of carbs can help prevent adverse GI symptoms
Stress less, anxiety and stress can contribute to loose stools among runners
Get in 5 servings of different fruits/vegetables daily
Challenge yourself to get in 30 unique plants every week to promote a diverse and recovered healthy gut microbiome
Notes From the Author: Kendra Weekley is a registered dietitian with a master's degree in exercise science, a Level 1 USA Triathlon coach, and a Certified Ironman coach. Kendra has been working in GI for the last three years and has been a registered dietitian for the last 10! Born and raised in Cleveland, you can find her enjoying local eateries and riding her bike in the MetroParks. Feel free to connect with Kendra about coaching or nutrition services, you can find her information at https://triiqcoaching.com/ or email at coachkendra@triiqcoaching.com
