Dana Eshelman, MS, RDN, METS I
The term “training your gut” describes a way to reduce the gastrointestinal (GI) stress that often occurs during training or race day. If you are an endurance athlete, chances are you have experienced this exercise-induced GI stress such as cramping, nausea, diarrhea, and/or vomiting.
Let’s take a step back and think about the physiology of digestion. Digestion normally occurs at rest when there is adequate blood flow to the gut allowing for absorption of nutrients and secretion of digestive enzymes. Exercise causes stress on the body and a shift in blood flow away from the gut causing changes in GI motility, absorption of nutrients, and secretion of enzymes that aid in digestion. This causes malabsorption and leads to a poor appetite, thus the athlete does not take in adequate hydration or fuel.
Unfortunately, under fueling and dehydration can cause additional GI distress and GI distress may be exacerbated by the intake of fuel and fluids during exercise. So, how does one tolerate more hydration and more fuel to support performance and prevent GI dysfunction? You train your gut!
What does “train your gut” mean?
There is a significant amount of research supporting the consumption of carbohydrates during exercise to maintain intensity and delay the onset time of exhaustion, especially at higher intensity. New research shows the gut is highly adaptable and can accommodate changes in your fueling through gene expression induced by sugar consumption. The evidence indicates there is a two to three week period of increasing carbohydrate intake during exercise to allow for adequate fueling and improved GI tolerance.
If you have had a poor experience (or many missed attempts) at fueling during exercise, you are not the odd one out. This is common. As the research shows, the body is adaptable and by practicing a fueling and hydration plan, you can improve your carbohydrate tolerance overtime. As with any nutrition plan, it is important to have a rehearsal of your fueling technique before race day. Your hydration plan is also of significant importance as this can help control GI distress and dehydration may exacerbate stress on the gut.
Proper Fueling + Training Your Gut The Academy of Nutrition and Dietetics recommends 30-60 grams of carbohydrate per hour of exercise and up to 90 grams of carbohydrate for endurance events lasting longer than three hours. If you are someone that trains fasted, or not eating anything pre-workout, starting off consuming 30-60 grams of carbohydrate before or during a workout may seem overwhelming and will likely cause GI distress. Here are some fueling techniques to train your gut:
Goal Nutrition + Hydration Pre workout
Pre workout 1-4 g/kg carbs in the 1-4 hours before exercise
1⁄2 piece of fruit + 1 T nut butter + 12- 16 ounces water OR 1⁄2 slice toast + 1 jam + 1 T nut butter + 12- 16 ounces water 12-15 grams carbs
1 piece of fruit + 1 T nut butter + 12- 16 ounces water OR 1 slice toast + 1 T honey + 1 T nut butter + 12- 16 ounces water 25- 30 grams carbs
1 piece of fruit + 1 T nut butter + 1 T honey + 1 slice toast + 12- 16 ounces water 50-60 grams carbs
During workout 30-60 g carb/ hour of exercise lasting longer than 1 hour
1-2 sports gummies OR 1⁄2 scoop drink mix in 32 ounces water 7-10 grams carbs
3 sports gummies OR 1 scoop drink mix in 32 ounces water 20- 25 grams carbs
6 sports gummies OR 2 scoops drink mix in 32 ounces water OR 3 sports gummies + 1 scoop drink mix in 32 ounces water 45-60 grams carbs
In the pre-workout phase you want to focus on adequate carbohydrate and low to moderate fiber, fat and protein foods. Carbohydrates are important for adequately fueling your muscles and topping off your energy stores, especially in workouts lasting longer than an hour. Fiber, fat and protein will slow down digestion, which we want to avoid pre-workout. These components should be consumed in meals and snacks throughout the day.
Pre-workout examples to work toward with 1- 4 hours before:
1 banana + 1 T nut butter (25 grams carb)
1⁄2 c oats + 1⁄4 c dried fruit (55 grams carb)
1 pita pocket + 2 T hummus (26 grams carb)
Small sweet potato + 1/4 c greek yogurt (20 grams carb)
Bob’s oat bar (28 grams carb)
1 c honey bunches of oats + almond milk (47 grams carb)
Dave’s Bread + 1 banana + 1 tsp honey (54 grams carb)
Pre-workout examples to work toward with 15- 45 minutes before:
1⁄4 c dried fruit (20 grams carb)
6 oz real fruit juice or sports drink (20-25 grams carb)
1 c fruit smoothie (20-25 grams carb)
Honey packet (15 grams carb)
During your workouts longer than 1 hour examples to work toward: **remember staying hydrated decreases GI distress
1 scoop drink mix + 32 ounces water such as Skratch, Maurten, Nuun Endurance or Tailwind (20-25 grams carb)
2 scoop drink mix + 32 ounces water (40-50 grams carb)
6 energy chews such as Honey Stinger, ProBar Bolt, or Skratch (~45 grams carb)
1 energy gel such as Untapped, Honey Stinger, Maurten, or GU (20-25 grams carb)
Start by evaluating your current hydration and fueling plan. Pick one area to target and build from there. Try a small snack pre workout, determine if that is enough or too much, adjust the timing of fueling and hydration, and continue to tweak based on energy, tolerance and workout goals. For workouts longer than one hour, add in hydration and fuel from the “Start Here” column above and decide if this is appropriate for your performance goals. Your fueling and hydration plan should be individual to you, and it often takes time to figure out your secret potion.
Keep in mind, just like training, not all days are treated equally; your fuel and hydration needs will vary from day to day. Adequate training of the gut with both carbohydrate and hydration leads to a less dramatic decrease of blood flow with increased exercise intensities, which is important in preventing GI symptoms.
If you are chronically experiencing GI distress with increasing training duration and intensity, you may consider consulting a sports dietitian to find your optimal fueling and hydration technique.