Ricardo Da Costa, initially a professional triathlete, encountered significant gastrointestinal issues during races in the 1990s, a common problem among his peers. These issues ranged from nausea to severe stomach pain, hindering athletes’ ability to consume water and nutrients during races and often leading to dropout. Recognizing the lack of attention to this problem, Da Costa pursued an academic career to delve into its roots.
Now an associate professor at Monash University in Australia, Da Costa focuses on understanding how food and nutrition impact sports performance. His research delves into how exercise affects digestion and how athletes can optimize their gut health to perform at their best. Over the past 15 years, he has become a renowned expert, attracting amateur and professional athletes worldwide to his laboratory for evaluation and treatment.
Da Costa’s work has revealed that exercise can significantly impact digestion, influenced by factors such as timing and intensity of workouts. While these effects can sometimes pose risks, most individuals can benefit from making small adjustments to their exercise routines to mitigate gastrointestinal issues. Whether amateur or professional, athletes can benefit from understanding and addressing these digestive challenges to optimize their performance.
How digestion works
Digestion is a complex process that begins even before food enters your mouth, according to Arafa Djalal, a gastroenterologist at the Icahn School of Medicine at Mount Sinai in New York.
The anticipation of food triggers the brain to signal the production of saliva and digestive enzymes in the mouth. As food enters the mouth, these enzymes, along with chewing, start breaking down the food to facilitate swallowing. From there, the food travels down the esophagus and into the stomach.
In the stomach, the food is subjected to a combination of relaxation and contraction, while digestive enzymes further break it down. This process typically lasts for two to five hours before the partially digested food moves into the small intestine, and then into the large intestine. Over the course of one to three days, undigestible remnants are eventually excreted.
As food enters the intestines, the body senses its presence and initiates the secretion of additional digestive enzymes. Peristalsis, the wave-like contractions of the intestines, helps gradually move the food through the digestive tract. This entire process requires energy, adequate blood flow, and coordination between various cells and organs in the body.
Moderate exercise
Moderate exercise can have positive effects on digestion and overall gut health. When you engage in low-intensity activities like walking or light workouts, it can help stimulate movement in your digestive system. Contracting your abdominal muscles, for example, can promote peristalsis in your intestines, facilitating the passage of food and waste.
While the muscles involved in digestion are involuntary and not under conscious control, physical activity can still aid digestion by increasing blood flow and promoting the contraction and relaxation of smooth muscles in the digestive tract.
In the long term, regular exercise contributes to maintaining a healthy gut environment, which enhances nutrient absorption. It also boosts the production of nitric oxide, a compound that helps relax intestinal muscles and reduces inflammation.
Moreover, exercise is known to benefit mental health by promoting the release of neurotransmitters and reducing stress, anxiety, and depression. Given that the gut and brain are interconnected, with nerve cells lining the intestines communicating with the brain, physical activity can positively influence gut-brain interactions. This is particularly relevant for conditions like irritable bowel syndrome (IBS), where stress and mental health play significant roles in symptom exacerbation.
While individuals with digestive disorders may find it challenging to exercise during flare-ups, incorporating physical activity into their routine during remission periods can provide relief from symptoms and improve overall well-being. Despite potential challenges, the benefits of exercise extend beyond digestive health, encompassing bone health, mental well-being, and overall quality of life.
High intensity exercise
High-intensity exercise poses unique challenges to digestion due to the increased demand for blood flow in muscles, lungs, and the heart. When exercising intensely, these systems compete for blood flow, leaving little available for the digestive system.
During low or moderate intensity exercise, blood flow can adequately support both digestion and physical activity. However, as exercise intensity increases, more blood is diverted to working muscles, lungs, and the heart, limiting blood flow to the digestive tract. Consequently, digestion becomes less efficient during high-intensity workouts.
Intense exercise also leads to the production of metabolic byproducts such as lactate and hydrogen ions as the body processes oxygen to create energy. During light exercise, these byproducts are easily cleared, but during high-intensity exercise, the body may struggle to eliminate them quickly enough. This can result in feelings of nausea or even vomiting, especially after short but intense bouts of activity.
The digestive system may attempt to expel these metabolic byproducts through vomiting, particularly following vigorous exercise sessions. Therefore, it’s not uncommon to observe individuals experiencing nausea or vomiting after engaging in highly demanding workouts, such as sprint races or intense training sessions.
Heat, dehydration, and bacteria
Heat exacerbates digestive issues during exercise by redirecting blood flow away from internal organs towards the skin for cooling. Sweating further contributes to dehydration, which thickens the blood and worsens digestive symptoms.
Intense exercise can also damage the intestinal lining, akin to how muscles experience microtears during workouts. Normally, this damage is repaired within 24 to 48 hours. However, excessively intense exercise can lead to significant damage that the intestines struggle to repair promptly. In severe cases, this may result in gut bacteria leaking into the bloodstream.
While the immune system can typically manage a small number of bacteria in the bloodstream, prolonged or intense exercise, especially beyond one’s usual limits, can overwhelm the immune system. This bacterial leakage poses a risk of severe illness or even death, particularly in individuals with weakened immune systems or those engaging in prolonged ultra-endurance activities like ultra-distance triathlons.
What you can do
To optimize digestion before exercise, it’s recommended to consume a small snack containing carbohydrates and sugars 30 to 60 minutes beforehand. Foods like bananas, toast, or carbohydrate drinks are ideal choices as they are quickly absorbed and provide fuel for the workout. These nutrients send signals to the stomach and intestines, encouraging them to maintain activity and recruit blood flow.
For endurance athletes, proper nutrition and hydration during exercise are crucial. Costa’s experience with a professional triathlete highlights the importance of gradually increasing fluid and fuel intake during training to train the digestive system alongside muscles. In the case of the triathlete struggling with digestive distress during Ironman races, Costa’s guidance helped him overcome his issues by adapting his nutrition and hydration strategies. As a result, he was able to successfully complete Ironman races and even achieved podium placements, demonstrating the significant impact of training the digestive system for endurance events.