Picture this: You’re running a race or on a long training run, and things are going really well. Then, all of a sudden it strikes you like a lightning bolt right in the guts. You have stomach cramping, pain, feel bloated or like you need to find the nearest public restroom or porta potty ASAP!
I hope you’ve never experienced this! But, the truth is that GI distress in endurance athletes is way more common than you may think. There’s a reason the old joke about never trusting a toot after mile 22 of a marathon exists. (All my marathoners know what I’m talking about here!) With endurance sports, gastrointestinal (GI) distress is something that can crop up at the worst of times, when you least expect it, or when you are least able to address it. The big question you may ask yourself if you’ve ever experienced something like this is “what caused that to happen”? And, the next question is very likely, “how can I avoid it ever happening again”?!
What is GI Distress?
GI distress is a collection of symptoms that includes digestive discomfort associated with bloating, stomachaches, sloshing, nausea, vomiting, reflux and diarrhea. It’s actually a fairly complicated matter, since the human body has a whole other nervous system devoted entirely to the function and regulation of the gastrointestinal nervous system. This is known as the enteric nervous system.
So many factors that are related to performance can, in fact, wreak havoc on GI function. When we are moving, our bodies must increase blood flow to our working muscles in order to meet their demand for oxygen. (Blood cells are kind of like oxygen Ubers and the muscles are their destination.) So, the body prioritizes blood flow to the muscles. This means that there is less blood flow to your gut, so your digestive system has a hard time digesting what you are eating.
Other causes of GI distress can include fiber, caffeine intake, nerves, under-fueling, osmolality, and carbohydrate sources (such as excessive fructose containing carbs) and amounts (often >90g cho/hr).
Wait a minute, did she just say osmolality?! What even is that?
The Role of Osmolality in GI Distress
Osmolality is a measure of the amount of dissolved particles in a fluid, like the sugar, carbohydrates, electrolytes, and even flavoring particles in your sports drink, for example. The role this plays in GI distress goes back to the physiology of the intestinal system. Depending on the osmolality of your drink, your stomach could have several different responses. But, the bottom line is that the formulation of your sports drink can have a real impact on how it is digested and utilized as a source of performance fuel. The osmolality of your drink should ideally be similar to the natural osmolality of your body fluids, which are intrinsically regulated.
Hydration and the Endurance Athlete
Another big factor that can impact your GI system is hydration, and it is tied into osmolality intimately. When you have a very high osmolality drink, you begin to see increased GI symptoms such as bloat, cramping, and gas. This is because the GI tract is not efficiently utilizing the contents of your drink. In fact, it is drawing water from your body to offset the osmolality of your drink and bring you closer to the natural levels of your body. Counterintuitively, this can delay the rehydration you hoped to achieve. It can also potentially cause dehydration and can negatively affect your performance, as well as cause those undesirable symptoms.
Hydration is often the biggest pitfall because carbs require water to be absorbed. So, if you are dehydrated, more water will be pulled from your body and cause further GI issues. It’s important to note that when you are taking on fuel during training, you should be utilizing a mix of carbohydrate sources. You should also be taking them on with adequate (but not excessive) hydration to avoid GI distress. On the flip side, if your osmolality is too low, your stomach doesn’t have enough particles (nutrients, electrolytes) but too much water. Then, the body will begin to pull nutrients from the muscles and elsewhere, causing cramping.
How to Prevent GI Distress in Endurance Athletes
While it all sounds super complicated, GI distress in endurance athletes is something that is actually quite manageable and even preventable if you follow some simple guidelines and test things out in your training periods.
Nutrition and hydration that doesn’t result in tummy trouble is a trial and error process, but can be so rewarding when you find the right mix for you. It is definitely something that you should experiment with during training so you have a nailed down strategy of what works (and what doesn’t!) for race day.
If you’re looking for more nutrition race guidelines that will help to reduce GI disturbances, check out our blog post on your race nutrition plan!
Do you have your race or long training nutrition plan dialed in? If not, we are here to help!
