EnlightenU Nutrition Consulting, LLC

Enlightening You about Food and Nutrition

Overcoming GI Distress During Exercise

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shutterstock_runner stomach problemsMost individuals are familiar with the lure and appeal of endurance activities. In fact, people seem to be coming out in droves to be a part a weekend marathon race, Ironman triathlon, or 100+ mile ultra-endurance events. However, what most of these people don’t hear about as they venture away from their comfy couch in hopes of a stronger, healthier body are some of the common side effects of gastrointestinal reflux (or heartburn), stomach cramps, nausea, bloating, vomiting and/or diarrhea. In fact, the majority of endurance athletes experience some gastrointestinal (GI) discomfort in their training or racing. Of course, these symptoms can be distressing and may affect performance. But, in some cases can be quite severe and result in needing to drop out of a race or discontinue the activity all together.

To keep your training and racing season enjoyable, check out some of the common causes of GI distress along with simple suggestions to help reduce symptoms.


The main causes of GI problems during exercise include:

  • Mechanical – The vibration or “jostling” of organs during strenuous activity, such as running or riding on rough pavement, may contribute to intraabdominal pressure and reflux, for example.
  • Physiological – Exercise reduces blood flow to the gut while directing blood flow to active tissues, such as the muscles, heart, lung and brain. Consequently, GI functions, such as the emptying of food and fluids from the stomach are affected.
  • Nutritional – A number of nutrition factors are known to contribute to greater GI distress, including too much fat, protein, and fiber; high concentrations of carbohydrate, especially fructose, lactose, and artificial sweeteners; caffeine and dehydration.

Additional factors such as anxiety, stress, and pre-race nerves can be a problem. Also, frequent consumption of aspirin, NSAIDS (ibuprofen) and antibiotics can negatively affect gut permeability and contribute to GI problems.


Most important is to practice your nutrition plan during training! It’s common for recreational athletes who decide to challenge themselves by training for longer events to neglect the role of nutrition in their preparation.  Too much focus on activity and exercise for weight loss rather than adequately preparing the body for the rigorous nature of the sport can backfire.  Athletes, who are not accustomed to fluid and food ingestion during exercise, struggle more with GI symptoms compared to those who consume fluids and food regularly during exercise.

To stay on track with your favorite activity, check out the following tips:

  • Limit intake of high-fiber foods the day before or morning of your activity or event. Fiber in foods, such as beans, lentils, high-fiber cereals/bread, and fruits and vegetables increases bulk and reduces transit time. Of course, consuming adequate fiber on a regular basis offers a number of health benefits; however, for athletes managing transit troubles, it is recommended to consume a low fiber diet the day or two before a race. Therefore, foods such white bread, white rice, plain bagels, canned or well-cooked fruits and vegetables may be more easily tolerated. A few fruits and veggies that are lower in fiber such as zucchini, cucumber (with skin removed), asparagus, tomatoes, grapes and grapefruit may also be tolerated.
  • Limit intake of fat and protein prior to activity or event. Foods containing fat and protein take longer to digest and can contribute to delayed emptying and stomach cramps. Try to consume meals at least 3 to 4 hours before an event.
  • Reduce or eliminate foods containing sugar alcohols (sorbitol, xylitol, erythritol, etc). Often found in “low carbohydrate” or “low sugar” foods, such as gum, candy, nutrition supplements or bars, this type of sugar can cause diarrhea.
  • Limit highly concentrated carbohydrate concentrations in foods or beverages. To avoid the accumulation of carbohydrate in the intestine, glucose (6%) or glucose plus fructose (8% to 10%) beverages are recommended. It can be especially important to avoid excessive intake of fructose, most notably in drinks or gels that are exclusively fructose. The ability of the human intestine to absorb fructose is limited, with 80% of people found to incompletely absorb 50 grams of fructose when ingested without other food (JADA, 2005). When fructose is consumed in the presence of glucose, absorption is enhanced.
  • Avoid dehydration. Start the race well-hydrated and ensure adequate fluid intake throughout the duration of the event. Dehydration as a result of loss of fluid from sweating is often associated with athletes struggling with GI complaints. This can especially be of concern during events when an athlete reduces intake because of being concerned or worried about suffering from GI problems.
  • Avoid trying any new foods or beverages the day of the event. Especially for individuals with a sensitive stomach or who frequently complain of problems, avoid consuming any unfamiliar foods or fluids the day of a big race.

If you follow the above recommendations and still have problems, try to keep a food and symptom journal to identify potential triggers. Eliminate suspicious foods for a week or two and then slowly re-introduce small portions and note whether the GI symptom resolves or persists. Continue to experiment with a wide variety of foods during training, allowing time for your gut to adjust. Learn what foods or fluids are most tolerable for you, and for best results, stick to your plan!

Author: EnlightenU Nutrition Consulting, LLC

I love food, family and fun! I also happen to be a Registered Dietitian and Board Certified as a Specialist in Sports Dietetics. My passion is to help people achieve their goals with food, eating and overall health, while learning how to live a life where they feel free to embrace their best unique self and confidently dismiss cultural messages of beauty and success.

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