Now, we know that while you may love Energy Nut Butter, when it comes to intense exercise, (such as a road half marathon, marathon, or cycle race), your fuel of choice is likely going to be rich in carbohydrates.
However, many of you may also experience the dark side of this approach during your athletic efforts, that have you bolting for the porta loos or trees. This is known as exercise-induced (or exercise associated) gastrointestinal (GI) symptoms. You may suffer from GI issues for a few reasons, including:
- Trying to consume more carbohydrates than your guts can handle. Most guidelines say 60 to 90 grams of carbs per hour of intense exercise that lasts more than 2.5 hours. Even elite athletes struggle to consume this amount!
- Redistribution of blood flow to muscles rather than your GI tract.
- Changes in GI nervous control.
Isabel Martinez from Monash University, recently published a systemic literature review, looking at studies that investigated the impact of gut training on athletes’ gastrointestinal response. That is, do certain gut training protocols help you to avoid or reduce gastrointestinal distress?
We’ve summarised some key takeaways from Isabel’s paper in a bite-sized, digestible form, with the hope that you don’t have to suffer from GI distress again!
What is Gut Training for Athletes?
Gut training is a way of conditioning and optimising the functioning of the gastrointestinal system to enhance performance.
By practicing your ideal nutrition intake or strategy for an event, gut training aims to improve your guts’ capacity to handle eating during exercise, enhance nutrient absorption and improve digestion - resulting in better gut comfort and improved physical performance.
Scientists have hypothesised that gut training can improve performance by:
- Reducing GI symptoms during exercise
- Improving the function of the GI tract and enhance the integrity of the gut lining
- Helping you to digest and absorb your fuel faster (i.e. improve gastric emptying, motility, and transport).
But do any of these actually help with performance?
Isabel’s literature review revealed that gut training can indeed improve gastrointestinal comfort and reduce GI symptoms when consuming both liquid and solid foods during exercise.
Specifically, it found that gut training enhanced “gastric load tolerance” – the volume of fuel that you can consume. Gut training can also increase the absorption of nutrients, resulting in faster transportation of carbohydrates from the intestines to your muscles.
Limitations of Gut Training for Athletes
From the studies that Isabel reviewed, gut training protocols that aim to enhance “gastrointestinal integrity” do not appear to be effective.
GI integrity refers to the health and proper functioning of your gut lining. It’s important to maintain GI integrity for optimal digestion, absorption of nutrients, and importantly – immune function. As a side-note, you can measure GI integrity by measuring specific plasma proteins which indicate whether epithelial cells in the intestine are ‘injured’.
Gut training is a worthwhile strategy to improve gut comfort and reduce GI symptoms during exercise.
Gut training may also improve the delivery of energy to your muscles and has been linked to improved endurance exercise performance. It is worth noting that maintaining gastrointestinal integrity remains crucial for optimal digestion, nutrient absorption, and immune function.
Overall, training your gut can improve your performance and avoid the dreaded tree-dash!
Check out our Coffee with Andrius video where Andrius outlines some practical strategies you can use to train your gut leading up to a race.
Gentle On The Gut
Read Isabel's systemic literature review and learn more about each of the individual studies here:
Martinez, I.G., Mika, A.S., Biesiekierski, J.R. et al. The Effect of Gut-Training and Feeding-Challenge on Markers of Gastrointestinal Status in Response to Endurance Exercise: A Systematic Literature Review. Sports Med 53, 1175–1200 (2023).