STOMACH TROUBLE: ‘RUNNERS TROT’

Gastrointestinal (GI) problems are very common in endurance athletes, and runners are particularly at risk.  Some athletes are more prone than others and symptoms range from mild to severe and effect performance on different levels.

The main reasons are believed to be:

• reduced blood flow to the GI tract is during exercise,
• the jarring effect of running,
• certain foods aggravating the bowel,
• anxiety around training or racing.

Reduced blood flow to the GI tract

During exercise blood flow is diverted to the exercising muscles and the skin (to aid with temperature control) and therefore away from the GI tract.  During very intense exercise this can be as much as 80% of blood flow.  This change in blood flow can result in a change in gut function (i.e. flow of contents through the GI tract) as well as the pressure of the sphincters that allow entry and exit from the stomach.  These are most likely to affect runners at very high intensities or interval training. 

Another probable effect of reduced blood flow is reduced absorption in the GI tract.  Ingested fluids and sugar (for hydration and as an energy source) may aggravate the gut and runners could experience

Nutrition

Nutrition can strongly influence GI distress, although many of the symptoms can persist in the absence of any food intake prior to or during exercise. The biggest culprits are fiber, fat, protein (specifically dairy) and fructose.  Very concentrated sugars in drinks, gels, sweets and other solid foods could also possibly increase GI problems.  Diluting your stomach contents by drinking water with these high sugar options is likely to reduce the likelihood of this happening.

‘Training your gut’ is important to help manage symptoms.  Athletes who mimic ‘race day’ nutrition strategies in training sessions significantly reduce their risk of developing GI symptoms during exercise. Research has shown that adaptations occur after just 20 days of consecutive feeding during exercise.  Including water, carbohydrate drinks and certain solids during training sessions can be an effective way in helping to reduce potential problems on race day.

Other contributing factors

Using certain pain relief medication, specifically non-selective non-steroidal anti-inflammatory drugs (NSAIDs) has been associated with GI problems during exercise.   

Managing GI problems

Outside of training/ rest:

• Athletes should include dietary fibre into their meals and snacks that are not close to the start of an exercise session.  Training sessions early in the morning make it easier to consume fibre during the day, however afternoon or evening sessions will mean having to limit fibre consumed for lunch and mid-meal snacks.
• Consider supplementing with probiotics.
• Keep a food and symptom diary to identify food or stress triggers.
•  Refer to a doctor or dietitian to rule out underlying gastrointestinal conditions or food intolerances such as lactose intolerance, gluten sensitivity, Irritable Bowl Syndrome (IBS) or Inflammatory Bowl Disease (IBD),
• Consider referring to a psychologist for stress management if necessary.

Around training:

• Avoid high-fructose foods (such as fruit juice).  However, fructose in combination with glucose may not cause problems and may even be better tolerated.  You will find this in some sports drinks which are most likely in tolerable proportions.
• Avoid high fat foods.  Fats take long to digest which slows down gastric emptying. High fat foods include fried foods, full fat dairy, cream, most dressings, sauces and gravies etc. (see article on ‘Nutrition Before Exercise’ for examples).
• Avoid high-fiber foods.  Fiber is generally not digestible, so high fibre foods will increase the contents moving through the intestine. Fibre is eventually fermented  by ‘good bacteria’ in the large intestine which causes gas production that may cause cramping. E.g. fruit that are eaten with skins (grapes, peaches etc.), salads, vegetables, high fibre cereals, legumes, corn, brown rice etc.
• Avoid milk products that contain lactose (i.e. milk, yoghurt, cream) as even mild lactose intolerance can cause problems during exercise. Choose lactose-free milk or milk alternatives such as soya, rice or almond milk.
• Avoid caffeine before and during competition. Caffeine can stimulate peristalsis/ bowel movement.
• Manage the volume of fluid.  Too much fluid as well as dehydration can worsen GI problems.  ‘Train’ the gut by having small amounts and slowly increasing volumes and frequency.
• Start with liquid foods i.e. meal replacement shake before exercise or electrolyte and carbohydrate drinks during exercise.  Drinks may need to be diluted initially, building up to the correct concentrations of carbohydrate and electrolytes as recommended on the product label.
• Progress slowly to solids before exercise, limit fibre, fat and protein. E.g. oats, white toast with honey or a banana. When progressing to solids during exercise, limit the more concentrated sources of carbohydrate such as gels. Start with small bites of a bar or individual sweets.
• Wash food down with water to help dilute stomach contents.
• Avoid aspirin and non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen. Both aspirin and NSAIDs have been shown to increase intestinal permeability and may increase the incidence of GI complaints. The use of NSAIDs in the pre-race period should be discouraged.