Have you ever experienced nausea, diarrhea, or other unpleasant digestive issues during or after a workout? You’re not alone! Exercise is good for your health, but it can be hard on your digestive tract in the short-term. Many athletes and active people experience digestive issues related to exercise. According to one study, the incidence ranges from 20 to 96% and the problem is more prevalent in women.
What kind of digestive issues are most common? Nausea, heartburn, diarrhea, abdominal pain, worsening of reflux symptoms, and even vomiting can occur in close proximity to a workout. Men and women who run are at the highest risk. Needless to say, symptoms like this can make a workout pretty uncomfortable. Who needs exercise to be harder than it already is?
Why are digestive issues so common during or after a workout? Exercise triggers short-term changes in central and peripheral nervous system activity that can impact intestinal motility and digestive function. Plus, exercise directs blood flow away from the digestive tract and toward the working muscles. In addition, physical activity causes changes to levels of gut hormones that circulate in the bloodstream. These can all affect how the digestive tract functions. To make matters worse, some people swallow air when they run or do a high-intensity workout. Swallowed air can cause bloating, burping, and gas. Runners are prone toward sucking in air, often unconsciously, and the more intense the workout, the more likely they are to take gasping breaths and swallow air.
Exercise-Induced Abdominal Pain
Let’s look at some of the more prevalent stomach problems related to exercise. One of the more common is called exercise-related transient abdominal pain or ETAP. If you have this exercise-related tummy problem, you might experience sharp abdominal pain, almost like a cramp, when you exercise. No one knows exactly what causes this common phenomenon, but it may be due to irritation and stress on the ligaments that support the abdomen or irritation of the outer layer of the abdomen. It’s usually short-lived and if it doesn’t resolve quickly after exercise, it’s important to get it checked out. One way to lower the risk is to not eat within 2 hours of exercise and avoid drinking sports drinks or other drinks with added glucose or salt.
A more serious condition is called exercise-induced intestinal ischemia. Fortunately, it’s not common. Exercise-induced transient ischemia involves a transient decrease in blood flow to the intestinal tract during exercise. A short-term decline in blood flow can cause a so-called “leaky gut” and release of proteins and enzymes into the bloodstream. People who have this condition may experience abdominal pain, nausea, bloating, and even rectal bleeding. This is a condition that requires medical attention and, in cases that don’t resolve, surgery. One way to lower the risk is to stay well hydrated at all times. Doing so helps ensure your intestines get adequate blood flow.
Acid Reflux and Heartburn
Up to 20% of athletes experience reflux and the symptoms often worsen during exercise. When you work out, you contract your abdominal muscles. That’s a good thing for your abs, but it increases the pressure inside your abdominal cavity. If you already have a weak sphincter or flap between the esophagus and stomach, it can cause acid to backflow into the esophagus. If you experience heartburn or acidity during exercise, you may have acid reflux that’s worsened by exercise. One way to lower your risk is to wait two hours after eating to work out and not eat large meals. Avoid eating a high-fat meal as fat slows the movement of food through the digestive tract. Also, don’t drink sugar or salty beverages before or during a workout. If you have frequent heartburn or acid reflux, talk to your doctor as there are medications that can help. Uncontrolled acid reflux can damage the lining of the lower esophagus in a way that increases the risk of esophageal cancer.
Diarrhea
One of the more inconvenient digestive issues you can experience when you work out is diarrhea. When you exercise, especially at a high intensity, it alters the activity of your nervous system in a way that can change bowel motility and bring on diarrhea. Also, taking non-steroidal anti-inflammatory medications, like ibuprofen, can alter the mucous lining of the digestive tract and cause exercise-induced diarrhea. This is more common in long-distance runners. If you’re prone towards diarrhea when you exercise, avoid eating a high-fat meal or a meal high in sugar before an exercise session.
Nausea
Nausea is a distinctly unpleasant feeling, especially when you’re working out. The reasons exercise can bring on nausea are varied. Sometimes, it’s due to acid reflux, but you may also experience queasiness if you eat before working out. Exercise reduces blood flow to the intestinal tract and slows stomach emptying. So, what you eat stays in your stomach longer. Eating a diet high in fat and fiber may worsen exercise-induced nausea since they further delay movement through the digestive tract. Try to wait at least two hours after a meal, and preferably three, before exercising. Avoid eating high-fiber or high-fat foods prior to a workout.
Drinking a lot of liquid, particularly liquids that contain carbs and sugar, can bring on nausea in some people. At the very least, the sensation of liquid sloshing around in your stomach is unpleasant. Coffee may help exercise performance, but some people experience nausea after drinking it. Be aware of your caffeine tolerance and don’t drink a lot of fluid just before a workout. Start hydrating several hours before. But, make sure you ARE well hydrated as mild dehydration can sometimes cause lightheadedness and nausea.
Bleeding from the Digestive Tract
Some people who run long distances experience microscopic loss of blood through their digestive tract. In fact, the incidence is between 8% and 28%. It’s not clear why this happens. One theory is that decreased blood flow to the intestinal tract during exercise slightly damages the wall of the intestine and triggers slight bleeding. This is more common in people who take non-steroidal anti-inflammatory medications before exercising.
The Bottom Line
Now you know some of the more common digestive issues people experience when they work out and why they occur. One step you can take to reducing your risk of digestive upset when you work out is to avoid eating within a few hours of exercise. Also, limit the size of a pre-workout meal or snack and keep it low in fat and fiber. If possible, avoid taking non-steroidal anti-inflammatory medications, including ibuprofen. Stay well-hydrated, but don’t drink a large quantity of water just before exercise or during a tough workout. If you have persistent digestive issues, see your physician.
References:
UptoDate.com. “Exercise-related gastrointestinal disorders”
Int J Sport Nutr Exerc Metab 2004; 14:197.
Sports Med 1998; 26:365.
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