I’ve been seeing more and more runners lately for symptoms of GI upset when running, or runners stomach. Can you relate? How many times have you been enjoying a run, only to have to stop due to cramping, nausea, gas or even reflux? Those symptoms can be very uncomfortable and cause distress in the runners gut. For some, it happens during longer runs only, and for others, it happens whenever they fuel. For others, it only happens during their goal race (go figure).
While some cases do require a more comprehensive approach (and perhaps seeing a doctor or GI specialist), many causes just require some lifestyle changes and awareness. This is a longer post so bear with me.
Today, I’m going to talk about some of the common reasons I see for runners stomach and how to treat them. Of course, what works for one person will not necessarily work for another. Which is why nutrition is such an individualized science, which is the cool part 🙂
What is Runners Stomach?
Runners stomach, or “runners gut,” refers to discomfort or gastrointestinal distress during exercise. Feelings such as nausea, reflux, burping or stomach pain are common.
Interestingly enough, runners are more likely than other athletes to experience runners gut. I found one study that mentioned the frequency of gastrointestinal distress and complaints are nearly twice as high during running compared to other endurance sports, like swimming or cycling.
GI disturbances can affect between 30-83% of runners, and as you may think, this can certainly hamper performance (1). We’ll talk about why this happens shortly.
Symptoms of Runners Stomach
These symptoms may manifest in the upper GI tract, with feelings of reflux or nausea. Or, you may even experience lower abdominal pain when running, or have symptoms of diarrhea. I know it’s not the most exciting topic to talk about, but it happens!
Why Do We Experience Runners Stomach?
Firstly, it’s helpful to understand how our bodies work during exercise. Normally, our blood flows to the stomach, or gut, to help with digestion. However, during a run, the brain diverts blood away from the stomach and towards the working muscles. Therefore, things tend to just “sit” in the stomach since our body doesn’t have many resources (or manpower) being put towards them. This can be uncomfortable for some.
Also consider that our abdominal muscles also go through a lot with the up and down motion of running, including altered motility and endocrine secretions. There are many theories as to why we may experience runners stomach and altered GI symptoms during running.
Some of these theories include:
- mechanical forces of running –> agitation of the gut
- fluid shifts
- decreased splanchnic blood flow
- changes in bowel transit time
- hormone shifts
- autoimmune changes
Here are some of the common nutrition reasons I see gastrointestinal distress in runners.
Now that we know blood flow is diverted from the gut during exercise, imagine having less blood flow period. Dehydration causes thicker blood, making it more difficult to flow. Progressive dehydration further decreases blood flow to the gut, causing even more gastrointestinal distress. The general rule is to avoid losing over 2% of your body weight during exercise, as it can lead to a slower delivery of nutrients and oxygen to cells, altered body temperature and muscle cramping. Dehydration can also affect performance, mental capacity and electrolyte balance.
Strenuous exercise and dehydration are the most common cause of gastrointestinal symptoms, according to a review published in the Current Opinion in Clinical Nutrition and Metabolic Care (2).
Improper Nutrient Timing
We want to eat something before exercise that our muscles can use, however we don’t want to eat the wrong kinds of foods. Before a run or workout, consider sticking to refined, fast-acting carbohydrates (white bread, white rice). Not only will they be digested quickly, they will also provide “quick energy” to use during the run.
Aim to eat larger meals 2-3 hours before a run to allow time to digest. Many runners also see success cutting out high fiber foods days before a longer run or race. If you can’t seem to figure out what foods are causing, keep a food journal and focus on reducing one high fiber food at a time before a run.
Improper Balance of Nutrients
Remember how blood is diverted from the gut to the working muscles during exercise? That means we typically don’t want to consume foods close to exercise that will “sit” in our stomach. If you suffer from lower abdominal pain when running, this may be more pertinent to you. Normally, we want to consume adequate fiber and healthy fats for our health and well-being. However, before exercise, they aren’t the best choice.
Fiber is a non-digestible carbohydrate, meaning it passes through our GI system undigested. This can result in gas production and cramping. Cruciferous vegetables, especially, tend to be huge promoters of gas and bloating, so I tend to tell athletes to stay away from those days before a long run or workout.
Similarly, fat takes a long time for our bodies to break down and may lead to feelings of sluggishness and discomfort during exercise. Probably best to eat these foods hours before exercise or save them for after to avoid stomach issues.
How to Treat Runners Stomach
Now, let’s discuss some nutritional strategies that may help with runners gut.
Make a Hydration Plan
Since hydration needs may vary by person, weather and environment, and how trained someone is, it’s difficult to give precise recommendations.
This post talks a little bit more about water needs during exercise. A good rule of thumb is to consume eight ounces of fluid 15-30 minutes before a run, and 16+ ounces a few hours prior. During a long run, drink to prevent thirst, although sometimes it can help to drink according to time. A good starting point is 0.4 to 0.8 liters per hour. After exercise, replenishing lost water is also crucial and it doesn’t have to just be through sports drinks. Chocolate milk can be a great way to rehydrate with electrolytes, too!
To make it more simple, to avoid dehydration, drink sufficient water before, during and after exercise. Add in adequate electrolytes during longer runs to maintain fluid balance. Running low on electrolytes, namely salt, can also result in nausea. If you’re a salty sweater, you may want to consider having a sweat test done with a professional, and adding salt tabs in either before or during a run.
Time Your Nutrition
This post goes into more detail about how to fuel for shorter vs. longer workouts. Stick with easier-to-digest carbohydrates before exercise, like toast or a banana. Some people may want to stick with simple carbohydrates (white toast) vs. complex carbohydrates (whole wheat toast) because they are likely to cause less discomfort.
For exercise under an hour, it’s usually not necessary to add fuel in during (more on this below). However, when you are fueling during workouts, I always recommend practicing different products and keeping a food journal to record any adverse symptoms. For example, you may feel better with an all-in-one powder mixed in with your water (like Tailwind or UCan), or you may prefer blocks, chews or gels. Or, foods that are easier on the stomach, like boiled salted potatoes, may serve you better. Experiment!
Generally, protein and fat are unnecessary during exercise, but protein is important for the recovery process after. Adding recovery foods, like tart cherry juice, turmeric and antioxidant-heavy foods, may help too.
Don’t Overdo Fat and Fiber Before Exercise
We discussed above why this is important. Fiber and fat are great for satiety, but not so great for fueling exercise. Perhaps the night before a long run or race, you cut down on the fiber and fat. That doesn’t mean you have to eliminate vegetables and whole grains all together. But, some forms of fiber, like cruciferous vegetables, tend to cause more gas than others. Also, cooking vegetables (rather than eating them raw), can also make them easier to digest and prevent some gastrointestinal distress.
I would avoid a colorful salad like this before exercise, but save it for after or the following day.
Consider Adding in Probiotic-Rich Foods and/or Supplements
Probiotics, also known as our live bacteria, may lower the incidence of GI symptoms apart from running, so it makes sense that they may also make your gut feel better during running. Probiotics can reduce inflammation and improve the response to oxidative damage, a by-product of running.
We do have some research demonstrating that they may improve endurance performance, as gastrointestinal health is important for regulating the adaptation to exercise. In a 2011 double-blind, randomized controlled trial, competitive cyclists who supplemented with Lactobacillus (a popular probiotic) saw reduced severity in gastrointestinal symptoms, compared with those taking a placebo (3).
So, are probiotics the cure to your gastrointestinal distress and lower abdominal pain when running? Probably not, but they may be a piece of the puzzle! There do seem to be modest benefits to including probiotics for performance, but more research needs to be done.
Either way, try including some probiotic-rich foods, like jerusalem arthichokes, kichi, sauerkraut, and cultured dairy and non-dairy yogurts into your diet to see if that helps with digestion and GI symptoms.
Include Adequate Electrolytes and Energy Throughout the Run
In most instances of distance running, we do need and require fuel and carbohydrates during exercise. Depletion of our carbohydrate and energy stores is associated with fatigue, reduced energy output (i.e performance decline), reduced skill and concentration and increased perception of effort (Source).
I usually recommend my runners to start with 30-60 grams of carbohydrates per hour over 75 minutes. This could mean about 2-3 gels/hour, or half gel every 10 minutes, whatever works. I recommend taking gels at regular intervals so your brain and body is receiving a steady flow of glucose.
For shorter runs and exercise under an hour, you generally don’t need to take anything for fuel. However, there are always exceptions to that. For instance, if you suffer from hypoglycemia or are working on (re)training your gut to handle carbohydrates during exercise, then it may be a good idea to have something. You also don’t want to wait too long to start fueling because the earlier you start, the easier it is for your gut to absorb nutrients without troubles. As you can see, it is a delicate balance.
If you are someone who suffers from gastrointestinal distress during running, it may be prudent to start practicing fueling and drinking very early in the run. Or, even practice fueling at regular intervals (i.e. – every 30 minutes) to see if it reduces symptoms.
Other Running and Nutrition Posts:
- Race Day Nutrition – The Ultimate Guide to Pre, During and Post Race Nutrition
- How Much Water Should You Drink When Training in the Summer?
- Sports Nutrition FAQs
- How Nutrition Helps with Recovery
- The best recovery foods for runners
- Fueling Differences For Longer and Shorter Races
I would love if you would share this post if you found it helpful!
- GI problems in distance running
- Impact of Physical Activity on GI Tract
- Lactobacillus fermentum (PCC®) supplementation and gastrointestinal and respiratory-tract illness symptoms: a randomised control trial in athletes
- Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance