Gastrointestinal issues (GI) in athletes can range from a little nausea, to lots of nausea and vomiting, a few cramps to ‘get me to a portapotty STAT’/aka diarrhea, and even worse – fecal blood loss (scary – I know this one first hand). Most of these issues involve hormones, electrolytes, blood flow, nutrition, hydration, gut motility, and even the nerves found in and around our gut.

The combination of runners + GI issues is common. It’s estimated that 1/3 to 1/2 of all athletes suffer from some kind of GI issue during training or competition. Add runners with celiac disease, irritable bowel syndrome (IBS) or disorders (IBD), lactose intolerance, or other food sensitivities and you have the perfect storm!

Gotta love the PortaPotty!

Depending on the complaint, there are some helpful nutrition strategies that may be worth experimenting with. I say “experimenting with” because what may help one person, might not necessarily help another. GI issues can be complicated, and it’s really a matter of paying attention to what’s going on with your digestive system:

  • Nausea, bloating and cramping, diarrhea/constipation and/or all of the above
  • What part(s) of the digestive system (stomach, intestines or colon)?
  • What types of foods are consumed (cooked vs raw)?
  • How much food and what time of day is food being consumed (On a full, empty, or semi-full stomach)?
  • As well as nutrient timing: what foods consumed before (<1 hr), during and after exercise (20-30 minutes)?
  • The quality and safety of foods eaten.

As you can see, it’s really about being a mindful eater, with special consideration regarding your exercise habits.

Here are some helpful suggestions for some of the more common complaints, such as GERD (gastroesophageal reflux disease), nausea and vomiting, bloating and gas, cramping and emptying, and the dreaded diarrhea. Of course, you want to experiment with foods and fluids during training – never on a race day.

GERD: aka, Gastroesophageal Reflux Disease; Heartburn; Dyspepsia:

  • Limit certain foods: High fat foods, Alcohol, Chocolate, Coffee, Juices, Peppermint
  • Hydrate well
  • Note pre-exercise nutrition and timing, and subsequent affects
  • Note affects of supplements (Gu’s, Chews, Protein bars, Herbs, Vitamins, Sport Drinks). Read labels – some supplements may be high in fat, fructose, or caffeine.


  • Avoid high fat and high calorie meals at least 3 hours pre-exercise
  • Pay attention to dehydration. Note temperature, sweat rate and altitude. To determine your sweat rate, weigh yourself pre-run and post-run. For every 1 lb lost, hydrate with 16 oz of water.
  • Avoid taking too many antacids containing sodium-bicarbonate.
  • Note affects of supplements (Gels, Chews, Herbs, Vitamins, Creatine and Amino acids, Sport Drinks)

Bloating and Gas:

  • Decrease consumption of carbonated beverages
  • Decrease cruciferous veggies (broccoli, cabbage, cauliflower)
  • Decrease consumption of beans, or make sure you soak beans overnight in a pot covered with water
  • Limit sugar alcohols (sorbitol, mannitol, Xylitol). Read labels!
  • Note food intolerances: FODMAPs, lactose (milk sugar) or fructose (fruit sugar)
  • Do you take in too much air when you eat or drink? Chewing gum can also increase the chance that you are taking in too much air.

Cramping and Emptying:

  • Emptying too Slow/Constipation: Make sure you are well-hydrated, and eating enough fiber (According to the Institute of Health, 38 g per day male, 25 g per day female)
  • Emptying too fast: Too much fiber? Too much fiber too close to exercise? Too many fatty foods? Too many of the same foods – and not enough variety?
  • Dehydration and/or concentrated carbohydrate foods and supplements like beverages, foods, or gels will promote a rush of fluid into GI tract
  • Food allergies and sensitivities: The Specific Carbohydrate Diet or FODMAPs


  • Identify and limit food triggers. These can be due to an auto-immune disease, food allergies, or food sensitivities.
  • Eating too many concentrated sweets (Re: sport supplements as listed in above)
  • Decrease certain foods pre-exercise: high fiber foods, fatty foods, fruit juices, sugar alcohols
  • Stick with more soluble fiber (oats, nuts, seeds, apples, bananas and blueberries) vs insoluble fiber (whole wheat breads and crackers, brown rice). Soluble fiber dissolves in water and forms a gel in the bowels, whereas insoluble fiber in your colon will be fermented by your gut flora/bacteria (hence the term pre-biotic) and can produce gas, or if hanging out there too long (like the whole time during your long run) may attract water and wind up giving you diarrhea.
  • Note Food Safety: Check out the USDA Food Safety Fact Sheets
  • Pay attention to dehydration. Dehydration can lead to diarrhea – it’s a Catch 22, so really pay attention to your hydration status.

 Of course, if you are experiencing intestinal bleeding, seek medical attention ASAP!

I hope this information helps – feel free to reach out to me to discuss further. If you have been diagnosed with ischemic colitis, IBD, or IBS, feel free to contact me – I would love to work on-on-one to address your symptoms, and correct them with appropriate medical nutrition therapy strategies so you can successfully reach all your race goals!


2015 Chicago Rock n Roll Half Marathon: 1st place age group win!