It’s the biggest race of your season. You’re nervous, but everything seems to be under control. But now your digestive system won’t cooperate. For a runner, what could be more unpleasant than having digestive problems during a run? Fortunately, there are solutions to help you prevent this issue. Here are five of them.
First, let’s explore the issue. Your digestive system is at its most vulnerable when you’re at peak physical exertion. When you run, blood is mainly directed to the muscles that are working to provide them with maximum oxygen. The digestive system then receives 70 to 80% less blood than normal. This results in damage and inflammation to the intestinal wall.
The impact of running does not just affect the bones, muscles and tendons – it impacts soft tissue such as your gastrointestinal tract, which in turn cause damage to the intestinal wall. These factors weaken the digestive system and can cause the runner to suffer intestinal discomfort during exertion. As the intensity or duration increases, so does the likelihood of a gastrointestinal issue.
Prevent, at Least a Little
Anything you eat may have something to do with the digestive problems you feel when you exercise. If you have food intolerance (e.g., lactose), it goes without saying that you should avoid problematic foods before a race.
Several other likely causes are under your control. Here are some precautions that can help you limit the damage.
- The time of your last meal
The problem: The presence of undigested food in the digestive system greatly increases the risk of discomfort.
How to prevent this: Allow at least 2 hours to digest a complete meal and at least 30 minutes for a snack.
- The composition of your last meal
The problem: A meal high in dietary fibre or fat tends to slow down digestion and therefore clogs the digestive system for longer periods of time.
How to prevent this: To make it easier to digest your pre-race meal, limit foods high in dietary fibre (whole-wheat bread, bran cereals, whole-grain pasta, etc.) and favour low-fat foods.
- Beverages and foods that are very sweet or salty during the race
The problem: To be properly absorbed, food and beverages must have sugar and salt (sodium) concentrations close to those in the blood. If they are too concentrated, they become difficult to absorb and the body tries to dilute them by moving water from the blood to the intestine. This excess water in the intestine is looking for the exit… increasing the risk of diarrhea. Note that fructose is absorbed at a 50% slower rate than glucose in your intestine. This means that if you consume fructose in excess compare to your absorption capacity, the concentration of fructose will remain higher in your intestin, increasing the likelihood of digestive problems. The maximum amount of fructose that can be absorbed by your intestin is 30 grams per hour
How to prevent this: When running for more than 90 minutes, choose sports drinks with a carbohydrate (sugar) concentration between 4 and 8% and a sodium content between 500 mg/l and 700 mg/l . Most sport drinks on the market respect this concentration. However, if you want to make your own drink, consult the Nutrition Facts table on the label of your favourite juice and measure a serving size that provides between 40 g and 80 g of carbohydrates. Make up the volume with water until you reach 1 liter (32 ounces) and finish by adding ¼ teaspoon of salt.
If you’re used to taking in energy gel or energy chews (or gummies) instead, make sure you ingest them with water to dilute their sugar concentration.
Also, break down your carbohydrate (sugar) intake into smaller portions throughout your run and gradually get used to it during your training sessions.
The combination of carbohydrates/sodium found in sports drinks and supplements facilitates absorption and improves the digestive tolerance of foods eaten during exercise. This is why it is still important to make sure that you have an adequate supply of electrolytes in these products. If you opt for solid foods, salted potatoes or pretzels are an interesting two-for-one option.
- Inadequate fluid intake
The problem: Dehydration increases the risk of digestive discomfort, but so does drinking too much. Indeed, problems occur in particular when the volume of liquid drank exceeds your body’s capacity to absorb it (about one litre per hour).
How to prevent this: Make sure you start the race well hydrated, but avoid drinking more than you need. Drink small amounts of water regularly during your run, paying attention to your thirst.
- Taking certain medications
The problem: Aspirin and non-steroidal anti-inflammatory drugs (NSAIDS, such as ibuprofen) increase intestinal permeability, allowing bacteria and large, partially digested food molecules to enter the bloodstream. This promotes an inflammatory response, increasing the risk of digestive problems.
How to prevent this: Talk to your doctor or pharmacist before taking medication while racing.
Digestive distress during exercise can make a huge difference in your performance. Good food planning beforehand is essential if you want to head straight to the finish line and avoid a little detour to the restroom!
Translation : William Chabot-Labbé
Isabelle Morin is a dietitian-nutritionist and has completed her diploma in sports nutrition with the International Olympic Committee. She is a lecturer at the University of Quebec in Trois-Rivières and collaborates with La Clinique du Coureur. You can meet with her in the Quebec City area or reach her via the internet. Visit her Facebook page.
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