OP-Ed: What’s New in Gut Health and Sports Nutrition?

Did you know the human gut does much more than digestion and absorption? The gut is home to immune cells, can communicate with the brain via the vagus nerve, and can feed off nutrients such as fiber to produce other beneficial bacteria and metabolites known as short-chain fatty acids (SCFAs). SCFAs include acetate, propionate, and butyrate and are utilized as fuel by colonocytes or are absorbed into the systemic circulation and can be used by other tissues as an energy source1. Think about how vital energy is to an athlete for optimal performance and the broader connection to sports nutrition; it’s quite fascinating!

Scientists have been making connections between this intersection of gut health and sports nutrition since the early 1980s, but recently, several scientific papers have described the gut as an athletic organ because of its adaptability during training, and it’s main function in delivering carbohydrates, fluid, and harboring energy from nutrients like fiber that undergo fermentation to deliver SCFAs2-4.

From scientific literature and experience in sports nutrition practice, we also know that the type of exercise may influence gut health and the microbiome makeup of athletes3. For example, low-to-moderate exercise can promote gastrointestinal (GI) motility and transit time and can help encourage greater microbial diversity. Exercise may also help increase the ratio of critical bacterial phyla like Bacteroidetes-Firmicutes, strengthen the intestinal barrier, and support GI immunity1-2. These are all tremendous benefits, but unfortunately, adaptations occur when exercise is vigorous and prolonged (≥2 hours). In this case, undesirable GI symptoms such as leaky gut, runner’s diarrhea, abdominal pain, and bloating can occur, and the big question is why.

Let’s break it down, shall we? In response to prolonged training, blood flow is prioritized to your working skeletal muscles, heart, and lungs. This means a decreased amount of blood flow to the gut. With this substantial decrease in blood flow, injury occurs to the lining of epithelial cells in your small intestine. 

In fact, the junctions between the epithelial cells become less tight, and an increase in gut permeability, or “leaky gut”, may occur. A leaky gut is undesirable because it allows for toxins, undigested food, and bugs to penetrate the tissues beneath it and enter the bloodstream4. Collectively, this creates a perfect storm for inflammation and an immune response, which can contribute to an increase in GI symptoms, illness, impaired nutrient absorption, and unfavorable changes in the gut microbiota. 

So much complexity exists in this space, and for athletes, the gut is largely impacted by diet and nutrition, so it is essential to properly nourish and support the athlete’s microbiome to the gut to help optimize performance. Athletes typically seek ways to gain a performance edge, and microbiome health is not often thought about in terms of gaining a competitive advantage.

As a practicing sports dietitian, properly preparing the gut for competition and discovering novel nutrition strategies for this population is so key! Supplementing with prebiotics, probiotics, and postbiotics for athletes are newer techniques I’ve incorporated into my practice to help support athletes’ gut health and performance journey.

About the Author

Renee Korczak Ph.D., RDN, CSSD, LD. Dr. Korczak is an advanced practice registered dietitian nutritionist with expertise in digestive health. Renee has her board specialty in sports dietetics and is an active voice in the sports nutrition and gut health space. Her research focuses on the intersection of gut health and sports nutrition. Outside of work, Renee enjoys time with her two children and husband. She enjoys travel, cooking, and fitness.

You can learn more about Dr. Korczak at her website, Premier Dietitian.


  1. Hughes RL, Holscher HD. Fueling Gut Microbes: A Review of the Interaction between Diet, Exercise and the Gut Microbiota in Athletes. Adv Nutr. 2021; 12(6):2190-2215. Doi:10.1093/advances/nmab077.
  2. Pugh JN, Lydon KM, O’Donovan CM, O’Sullivan O, Madigan SM. More than a gut feeling: What is the role of the GI tract in female athlete health? Eur J Sport Sci 2022; 22(5): 755-764. Doi: 10.1080/17461391.2021.1921853.
  3. Mohr AE, Jager R, Carpenter KC, et al. The athletic gut microbiota. J Int Soc Sports Nutr. 2020; 17(24).
  4. O’Brien MT, O’Sullivan O, Claesson MJ, Cotter PD. The Athlete Gut Microbiome and its Relevance to Health and Performance: A Review. Sports Med 2022; 52(S1): 119-128. Doi:10.1007/s40279-022-01785-x.