Gut Health for Endurance Athletes: Gut Training, Probiotics, and Recovery

For endurance athletes, the gut is more than just a digestive organ—it is a critical component of performance, recovery, hydration, and fueling success.

Many endurance athletes experience gastrointestinal (GI) symptoms during training or competition, including nausea, bloating, cramping, diarrhea, reflux, and stomach discomfort. In fact, studies suggest that up to 70% of endurance athletes experience GI symptoms at some point during training or racing (de Oliveira & Burini, 2009).

Understanding the relationship between endurance exercise and gut health can help athletes reduce symptoms, improve fueling tolerance, and support recovery.

What Happens to the Gut During Endurance Exercise?

During prolonged exercise, the body prioritizes blood flow to working muscles, the heart, lungs, and skin. As a result, blood flow to the gastrointestinal tract can decrease substantially.

Research suggests that splanchnic blood flow may decrease by as much as 80% during intense endurance exercise (van Wijck et al., 2011).

This reduction in blood flow is known as exercise-induced gut ischemia.

When blood flow to the digestive tract is reduced:

• Nutrient absorption may be impaired

• Intestinal barrier function may be disrupted

• GI symptoms may increase

• Gut permeability may increase

This phenomenon helps explain why athletes often experience GI distress during long runs, races, and hard training sessions.

Exercise-Induced Gut Ischemia

Gut ischemia occurs when the gastrointestinal tract receives insufficient blood flow during exercise.

Research suggests exercise-induced ischemia may contribute to:

• Nausea

• Abdominal cramping

• Urgency

• Diarrhea

• Bloating

• Increased intestinal permeability

(van Wijck et al., 2011)

Some athletes may be more susceptible than others, particularly during:

• Long-duration events

• Hot-weather training

• Dehydration

• High-intensity efforts

• Inadequate fueling

Understanding these risk factors can help athletes proactively manage symptoms.

What Is Gut Training?

Many athletes train their muscles, heart, and lungs—but forget to train their gut.

Gut training refers to the process of gradually exposing the digestive system to carbohydrates and fluids during exercise so that the gastrointestinal tract becomes more efficient at handling fuel during competition (Jeukendrup, 2017).

Just as muscles adapt to training, the gut appears capable of adaptation as well.

Research suggests gut training may:

• Improve carbohydrate absorption

• Reduce GI symptoms

• Increase fueling tolerance

• Improve race-day nutrition success

(Jeukendrup, 2017)

How to Practice Gut Training

During long runs or rides:

• Practice consuming carbohydrates during training

• Use race-day nutrition products during training

• Gradually increase carbohydrate intake

• Practice hydration strategies

• Avoid trying new products on race day

Athletes who consistently train their gut often report fewer GI issues during competition.

Probiotics and Endurance Performance

The gut microbiome consists of trillions of microorganisms that influence digestion, immune function, metabolism, and overall health.

Emerging research suggests probiotics may provide benefits for endurance athletes, particularly regarding GI health and immune support (Jäger et al., 2019).

Potential benefits include:

• Improved gut barrier integrity

• Reduced GI symptoms

• Enhanced immune function

• Reduced incidence of upper respiratory infections

• Improved recovery support

While probiotics are not a magic performance supplement, they may help support training consistency by reducing illness and GI disruptions.

Food Sources That Support Gut Health

A healthy gut microbiome thrives on dietary diversity.

Foods that support gut health include:

Prebiotic Foods

Prebiotics feed beneficial gut bacteria.

Examples include:

• Oats

• Bananas

• Onions

• Garlic

• Asparagus

• Legumes

Fermented Foods

Fermented foods contain beneficial microbes.

Examples include:

• Yogurt

• Kefir

• Sauerkraut

• Kimchi

• Miso

• Tempeh

Fiber-Rich Foods

Dietary fiber supports microbial diversity and production of beneficial short-chain fatty acids.

Examples include:

• Fruits

• Vegetables

• Whole grains

• Beans

• Lentils

Nutrition Strategies to Support Gut Health During Training

Athletes should focus on daily habits rather than a single supplement.

Helpful strategies include:

• Meeting daily carbohydrate needs

• Consuming adequate energy

• Staying hydrated

• Training the gut regularly

• Including probiotic and prebiotic foods

• Practicing race-day fueling during training

• Avoiding drastic dietary changes before competition

Consistency matters more than perfection.

References

de Oliveira, E. P., & Burini, R. C. (2009). Food-dependent, exercise-induced gastrointestinal distress. Journal of the International Society of Sports Nutrition, 6(1), 27. https://doi.org/10.1186/1550-2783-6-27

Jäger, R., Mohr, A. E., Carpenter, K. C., Kerksick, C. M., Purpura, M., Moussa, A., Townsend, J. R., West, N. P., Black, K., Gleeson, M., Pyne, D. B., Wells, S. D., & Arent, S. M. (2019). International Society of Sports Nutrition position stand: Probiotics. Journal of the International Society of Sports Nutrition, 16(1), 62. https://doi.org/10.1186/s12970-019-0329-0

Jeukendrup, A. E. (2017). Training the gut for athletes. Sports Medicine, 47(Suppl 1), 101–110. https://doi.org/10.1007/s40279-017-0690-6

van Wijck, K., Lenaerts, K., van Loon, L. J. C., Peters, W. H. M., Buurman, W. A., & Dejong, C. H. C. (2011). Exercise-induced splanchnic hypoperfusion results in gut dysfunction in healthy men. PLoS One, 6(7), e22366. https://doi.org/10.1371/journal.pone.0022366