ASK THE SPORTS DIETITIAN RHIANNON SNIPE is an Accredited Practising Dietitian (APD), Provisional Sports Dietitian and Founder of Energetix Nutrition and Fitness. Rhiannon has competed in running events for over a decade, completing five marathons and five Ironman-distance triathlons (including two world championships). She accredits a large portion of her success as an endurance athlete to her training and race nutrition.
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Q What is causing my tummy troubles when I run?
A Gastrointestinal (GI) problems, also known as “runner’s trot” affects up to 90% of runners. It can cause decreased performance or withdrawal from competition. Lower GI symptoms (such as stomach cramps, flatulence, urgency and diarrhoea) seems to occur more frequently in running than in other sports; however, runners can also experience upper GI symptoms (such as belching, nausea and vomiting). Identifying the cause of GI problems is complex due to its multi-factorial nature. Despite this complexity, and in the absence of an underlying medical condition, the cause is often attributed to factors related to nutrition intake or the physical effects of the exercise itself.
Nutrition-related causes
What, when and how much you eat and drink before and during exercise is linked with GI complaints during running and endurance exercise. Foods high in fat, fibre and protein are more slowly digested and are associated with increased risk of GI symptoms; while the timing of your pre-exercise meal is another important consideration for achieving adequate digestion (see fact sheet Eating and Drinking Before Sport). Other nutrition-related factors that affect the GI system during exercise include carbohydrate intake (type, amount and concentration), hydration status and the use of aspirin and non-steroidal anti-inflammatories (NSAIDs).
Physiological and mechanical causes
A major contributor to GI problems is believed to be the redistribution of blood away from the GI tract to the working muscles during exercise. This redistribution of blood flow can be highly variable since it is influenced by factors such as age (younger athletes have further reduction in blood flow), fitness level, exercise intensity, thermal stress and hydration status. A prolonged reduction in blood flow has been shown to damage the lining of the GI tract. The mechanical jarring from the impact of running has also been shown to damage the lining of the GI tract. It should be noted that psychological stress such as pre-race anxiety may also cause GI disturbances in some athletes.
So what can I do about it?
An effective solution revolves around managing the above stressors through appropriate training and nutritional intake. A consult with an Accredited Sports Dietitian may be beneficial to address any nutrition-related causes of GI symptoms.
Note: If your gastrointestinal problems are not specifically exercise-related then it would be beneficial to see your GP first to identify any underlying medical causes and then follow up with an Accredited Sports Dietitian.
