By: Josilyn Cordes (intern) and Orli Rabin of ThrivingBiome
Did you know that your body hosts trillions of microorganisms that play a crucial role in keeping you healthy? Among these are probiotics- which are beneficial microbes that support digestion, immunity, and more.
Your gut contains a diverse ecosystem of bacteria, archaea, and eukarya, collectively known as the gut microbiome. Over thousands of years, the microbiome has evolved to form a mutually beneficial relationship with our bodies, influencing digestion, immunity, and even mental well-being. With all the talk on gut microbiome and its importance, it’s crazy to think that research on this topic is still in its early stages and we are only now beginning to uncover the full extent of its impact on our health.
Understanding the gut microbiome and the role of probiotics is especially relevant to endurance athletes, who often face digestive issues that can impact comfort and performance. Let’s dive in!
Why do endurance athletes experience GI issues?
Endurance athletes are more prone to gastrointestinal (GI) issues due to a combination of physiological, mechanical, and nutritional factors that put stress on the digestive system. A study found that 96% of ultramarathon race participants experienced some form of gastrointestinal symptoms (ex. belching, nausea, or vomiting) during the race and 36.5% of non-finishers attributed their failure to these symptoms. To understand why these symptoms are so common, it's important to look into what happens to our body during intense exercise.
During long workouts, lood is pulled away from the gut to the muscles, which can cause nausea, cramping and diarrhea. Running and high impact workouts cause mechanical stress, while sweating causes fluid and electrolyte loss which results in slow digestion. Many sports drinks and energy gels, especially those high in fructose, can worsen these symptoms by pulling water into the intestines leading to bloating and discomfort. Heat stress occurs when the body’s core temperature rises due to prolonged exposure to high temperatures or intense exercise. This is also a factor that plays a role by raising gut inflammation and triggering digestive issues.
Given the high risk of digestive issues among endurance athletes, finding ways to support gut health is essential to optimize comfort and performance. This is where probiotics and probiotic rich foods may offer benefits.
How do probiotics support athletic performance?
Improved Digestion & Nutrient Absorption
Endurance athletes have higher energy and nutrient demands. Probiotics support digestion by aiding in the breakdown of complex carbohydrates, proteins, and fats more effectively. Certain probiotic strains contain enzymes that assist in this process, which can lead to better absorption of nutrients like protein (muscle repair), iron (oxygen transport), and B vitamins (energy production). A balanced gut microbiome can make it easier to meet nutrient needs without digestive distress.
Enhanced Immune Function
Intense training can suppress immune function by impacting changes in lymphocyte numbers and functions, which can impair the body's ability to fight infection, leaving the athlete more prone to illness. Probiotics help strengthen the immune system by stimulating the production and activity of immune cells (natural killer cells and T cells) which play a role in defending the body against infection or illness. Additionally, certain probiotics help regulate inflammation, preventing excessive inflammatory responses that could weaken the immune system. Research has shown that probiotics can reduce the frequency of upper respiratory tract infections (URTIs), such as colds or sore throats, which are common during times of intense training. A diverse gut microbiome contributes to a more resilient immune system, which helps athletes stay healthy and maintain consistent performance.
Gut Barrier Protection & Reduced Inflammation
Long training sessions and intense competitions can put stress on the body in many ways, including the digestive system. One of the issues athletes often deal with is increased gut permeability which is also known as leaky gut. This condition occurs when the lining of the intestines become damaged, allowing harmful substances like bacteria, toxins, and undigested food particles to enter the bloodstream. This increase in gut permeability is thought to result from reduced splanchnic blood flow and heat stress during prolonged exercise, which in return compromises the integrity of the intestinal epithelial barrier and leads to the translocation of endotoxins such as lipopolysaccharides (LPS) into systemic circulation. An immune response is then triggered causing symptoms like digestive issues and systemic inflammation throughout the body. Probiotics help protect the gut barrier by supporting the integrity of the intestinal lining. Certain probiotics stimulate the production of mucous, which acts as a protective layer over the gut lining. In addition to maintaining the gut barrier, probiotics help regulate the body’s inflammatory response by producing short-chain fatty acids, such as butyrate, which have anti-inflammatory properties and help calm the immune system. This reduces gut inflammation and can improve overall digestive health, making it easier for athletes to train and compete without digestive discomfort.
Potential Impact on Endurance & Recovery
Certain probiotic strains have been shown to support endurance performance and recovery by influencing several physiological processes. While more research is still needed, many studies suggest that probiotics can help improve endurance performance in athletes and reduce exercise-induced stress and muscle damage. As previously mentioned, probiotics help regulate inflammation in the body, which is especially important after intense workouts or competitions. High-intensity training can cause muscle damage and increase markers of inflammation, like cytokines. Probiotics, particularly strains such as Lactobacillus and Bifidobacterium, may help reduce these inflammation markers, leading to less muscle soreness and enhanced recovery. This reduction in inflammation can help athletes return to training faster and with less discomfort.
In addition to supplements, athletes can also support gut health by dietary choices, including whole foods that naturally contain probiotics.
Whole Food Sources of Probiotics
While supplements can be effective, food choices often provide a more natural and sustainable approach to supporting gut health. Whole foods that are fermented or cultured such as yogurt, kefir, sauerkraut, kimchi, miso, tempeh, and kombucha contain a wide variety of beneficial bacteria that help promote a balanced gut microbiome. An additional benefit to whole food choices is that they also provide other nutrients such as fiber, vitamins, and minerals, which work synergistically to improve digestion and enhance immune function. Regularly consuming probiotic rich foods helps foster a diverse gut environment, which may lead to long-term digestive health benefits, improved nutrient absorption, and better overall health. By focusing on whole food sources, athletes can ensure their body receives a consistent supply of probiotics while also benefiting from the other nutrients provided by these foods. Incorporating these whole food sources into an athletes’ diet can have a significant impact on recovery and overall health. However, for those looking to optimize their gut health further, understanding which specific probiotic strains are most beneficial for endurance athletes can make a difference.
Incorporating these whole food sources into an athletes’ diet can have a significant impact on recovery and overall health. However, for those looking to optimize their gut health further, understanding which specific probiotic strains are most beneficial for endurance athletes can make a difference.
Best probiotic strains for endurance athletes (backed by science)
We know that probiotics can help us recover fast and keep our gut and immune system in top shape. However, not all probiotics are created equal. Here is a breakdown of top probiotic strains backed by research for endurance athletes.
Reduces exercise induced inflammation and oxidative stress
Enhances neurotransmitter balance
Improves mental focus and aids in recovery
Research suggests that supplementation with Lactobacillus Plantarum PS128 significantly alleviated oxidative stress and inflammation markers (creatine kinase, thioredoxin, myeloperoxidase), increased plasma branched amino acids, suggesting improvement in nutrient absorption, and may also serve as a beneficial ergogenic acid to help improve performance.
Reduces the risk of upper respiratory tract infections (URTIs)
Current research shows that Lactobacillus Rhamnosus modulates immune function by enhancing dendritic cells and increasing mucosal T cells, which in turn may contribute to a reduced incidence of upper respiratory tract infections.
Studies show that supplementing Lactobacillus casei Shirota may help reduce the incidence of upper respiratory tract infections during intense training by maintaining higher levels of salivary immunoglobulin ( IgA), therefore supporting mucosal immunity and reducing infection risk, particularly during the winter months.
Bifidobacterium longum 35624 regulates inflammation by promoting regulatory T cells, enhances immune response by increasing pro-inflammatory markers like TNF-α and IL-6, and may also improve cognitive outlook under stress by supporting recovery and mental resilience, as evidenced by its effects in athletes undergoing intense physical training.
Bottom line: Should endurance athletes use probiotic supplements?
When you are participating in intense training, logging miles, and pushing your body to its limits, your gut and immune system often take a hit. That’s where probiotics can come into play, especially those with well researched strains- can help athletes handle the stress of training and competition more effectively.
That being said, while probiotics can offer significant benefits for endurance athletes by supporting gut health and immune function, it's’ important to consider potential underlying issues like gut dysbiosis (an imbalance in gut bacteria) or small intestinal bacterial overgrowth (SIBO) which can impact digestive health and performance and actually make it so that you feel worse while on a probiotic supplementation.
Dysbiosis and SIBO
Gut dysbiosis and small intestinal bacterial overgrowth (SIBO) change the game when it comes to probiotic supplementation, especially when it comes to endurance athletes. While probiotics can offer a wide variety of benefits, they should be approached carefully in these cases. Here are some recommendations tailored for endurance athletes with gut dysbiosis or SIBO:
Address underlying gut issues first
If you are training intensely while dealing with gut dysbiosis or SIBO, work with a functional medicine or GI- trained provider to prioritize gut-restoring nutrients and address underlying gut issues first.
Avoid random over the counter probiotics
Many general probiotic blends contain strains that ferment carbohydrates in the small intestine, potentially worsening symptoms of SIBO. Avoid multi-strain probiotics and formulas with prebiotics unless cleared with a medical professional.
Focus on spore-based or soil-based probiotics
Spore-forming probiotics like Bacillus coagulans and Bacillus subtilis are less likely to ferment in the small intestine- making them better tolerated by those with gut dysbiosis or SIBO.
Use single-strain supplements (if any)
Certain probiotic strains may help but should be introduced one at a time and under supervision.
Start with a low dose and increase slowly as tolerated
Conclusion
As an endurance athlete, your gut health isn’t just about digestion. It’s a critical player in your recovery, immunity, energy, and even mental clarity. The right probiotic can give you a competitive edge, helping you go the distance while minimizing setbacks. However, it is important to remember that probiotics are not one-size-fits-all. Strains, dosage, and timing can vary depending on your training load, diet, and personal gut microbiome. While supplements can be helpful, prioritizing whole food sources of probiotics like yogurt, kefir, sauerkraut, miso, and tempeh can also support a diverse microbiome while providing you with other vital nutrients like fiber, vitamins, and minerals. Working with a Registered Dietitian can be helpful in navigating these options to build a personalized approach that supports both you and your long-term health.
Stuempfle KJ, Hoffman MD. Gastrointestinal distress is common during a 161-km ultramarathon. J Sports Sci. 2015;33(17):1814-1821. doi:10.1080/02640414.2015.1012104
Jäger R, Mohr AE, Pugh JN. Recent advances in clinical probiotic research for sport. Curr Opin Clin Nutr Metab Care. 2020;23(6):428-436. doi:10.1097/MCO.0000000000000686
Łagowska K, Bajerska J. Probiotic supplementation and respiratory infection and immune function in athletes: systematic review and meta-analysis of randomized controlled trials. J Athl Train. 2021;56(11):1213-1223. doi:10.4085/592-20
Varghese S, Rao S, Khattak A, Zamir F, Chaari A. Physical exercise and the gut microbiome: a bidirectional relationship influencing health and performance. Nutrients. 2024;16(21):3663. doi:10.3390/nu16213663
Huang W-C, Lee M-C, Lee C-C, et al. Effect of Lactobacillus plantarum TWK10 on exercise physiological adaptation, performance, and body composition in healthy humans. Nutrients. 2019;11(11):2836. doi:10.3390/nu11112836
Sivri D, Şeref B, Bulut MŞ, Gezmen Karadağ M. Evaluation of the effect of probiotic supplementation on intestinal barrier integrity and epithelial damage in colitis disease: a systematic review. Nutr Rev. Published online 2024. doi:10.1093/nutrit/nuae180
Walsh NP. Nutrition and athlete immune health: new perspectives on an old paradigm. Sports Med. 2019;49(Suppl 2):153-168. doi:10.1007/s40279-019-01160-3
Carbuhn AF, Reynolds SM, Campbell CW, et al. Effects of probiotic (Bifidobacterium longum 35624) supplementation on exercise performance, immune modulation, and cognitive outlook in Division I female swimmers. Sports (Basel). 2018;6(4):116. doi:10.3390/sports6040116
Huang H-Y, et al. Long term supplementation of Lactobacillus plantarum PS128 attenuated high-intensity exercise induced acute-phase inflammation in triathletes. Curr Dev Nutr. 2020;4(Suppl 2):nzaa062_021.
Majeed M, Nagabhushanam K, Paulose S, Arumugam S, Mundkur L. The effects of Bacillus coagulans MTCC 5856 on functional gas and bloating in adults: a randomized, double-blind, placebo-controlled study. Medicine (Baltimore). 2023;102(9):e33109. doi:10.1097/MD.0000000000033109
Vargas N, Marino F. Heat stress, gastrointestinal permeability and interleukin-6 signaling - Implications for exercise performance and fatigue. Temperature (Austin). 2016;3(2):240-251. Published 2016 Apr 28. doi:10.1080/23328940.2016.1179380
