Probiotics and Athletic Performance: Gut Health Meets Sports
Intensely training athletes push their bodies to extreme limits. Yet it is often forgotten that the digestive tract is one of the first organs to suffer under excessive strain. Research in recent years has shown that probiotics may be an important addition to the athlete's toolkit.
Intense Training and the Gut Barrier
High-intensity exercise — particularly prolonged endurance activities like marathons or triathlons — can cause a phenomenon known as "leaky gut." This means that:
- Intense physical effort redirects blood to muscles and away from the digestive tract
- The intestinal mucosal barrier temporarily becomes more permeable
- Toxins and bacteria can enter the bloodstream
- This triggers an inflammatory response that slows recovery
Many marathon runners and triathletes experience this as GI (gastrointestinal) symptoms — nausea, abdominal cramps, and diarrhoea.
ISSN Position Stand: Jager et al. 2019
The International Society of Sports Nutrition (ISSN) published an official position stand on probiotics in sport in 2019. Key conclusions from the Jager et al. (2019) document:
- Probiotics may reduce the severity and duration of upper respiratory tract infections in athletes
- Certain strains support gut barrier integrity during intense training
- Probiotics are generally safe for athletes
- Effects are strain-specific — not every probiotic delivers results
This was an important milestone because, for the first time, a prestigious sports nutrition organisation gave official support to probiotic use among athletes.
Studied Strains in Athletes
Lactobacillus acidophilus NCFM
This is one of the most studied strains in the athletic context:
- Has shown potential for reducing upper respiratory tract symptoms during training periods
- Good survivability in the digestive tract
- Widely available and well-tolerated
Bifidobacterium lactis Bi-07
Often used alongside L. acidophilus NCFM:
- Supports immune function
- Has shown synergy with NCFM in athlete studies
- Helps maintain gut microbiome balance during intense training
Marathon and GI Symptoms: Pugh et al. 2019
Pugh et al. (2019) conducted an important study with marathon runners, producing results of practical interest:
- Probiotic supplementation reduced GI symptoms during marathon running
- Participants reported less nausea, cramping, and digestive discomfort
- The effect was noticeable both during the training period and on race day
This study was particularly valuable because GI symptoms are one of the primary reasons marathon runners consider dropping out.
Supporting Recovery
A growing body of evidence suggests that probiotics may also support recovery after intense training:
- Reducing inflammation: certain strains may influence inflammatory markers
- Nutrient absorption: a healthy gut absorbs proteins, carbohydrates, and micronutrients more efficiently
- Immune function support: overtraining suppresses the immune system; probiotics may partially mitigate this
Probiotics and Protein: A Synergistic Relationship
An interesting aspect for athletes — gut health directly affects protein absorption:
- A healthy gut absorbs amino acids more efficiently
- This translates to better protein synthesis and recovery
- Combining probiotics with protein powder may be a strategic approach
Practical Guide for Athletes
When to start:
- Ideally, begin probiotics at least 2 weeks before a major competition
- Regular daily intake yields better results than sporadic use
What to look for:
- Choose strains tested in athletes (L. acidophilus NCFM, B. lactis Bi-07)
- Minimum 10 billion CFU per day
- Monitor your individual response — some athletes' digestive systems need an adjustment period
What to avoid:
- Do not try a new probiotic for the first time on race day
- Do not exceed the recommended dosage
Summary
Intense training stresses the digestive tract and can damage the gut barrier. The Jager et al. (2019) ISSN position stand supports probiotic use in athletes for respiratory health and gut barrier protection. Pugh et al. (2019) showed that probiotics reduce GI symptoms during marathons. A strain-specific approach is essential — L. acidophilus NCFM and B. lactis Bi-07 are the most studied in athletes.
Dietary supplements are not a substitute for a varied, balanced diet and healthy lifestyle.
References
- Jager, R., Mohr, A.E., Carpenter, K.C., Kerksick, C.M., Purpura, M., Moussa, A., Townsend, J.R., Lamprecht, M., West, N.P., Black, K., Gleeson, M., Pyne, D.B., Wells, S.D., Arent, S.M., Smith-Ryan, A.E., Kreider, R.B., Campbell, B.I., Bannock, L., Scheiman, J., Wissent, C.J., Pane, M., Kalman, D.S., Pugh, J.N., ter Haar, J.A. & Antonio, J. (2019). International Society of Sports Nutrition Position Stand: Probiotics. Journal of the International Society of Sports Nutrition, 16(1), 62.
- Pugh, J.N., Sparks, A.S., Doran, D.A., Fleming, S.C., Langan-Evans, C., Kirk, B., Feber, K. & Close, G.L. (2019). Four weeks of probiotic supplementation reduces GI symptoms during a marathon race. European Journal of Applied Physiology, 119(7), 1491-1501.
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