Gastrointestinal Distress (GI Distress)
I take a look at GI distress, how it’s caused and why you should think about it.
Gastrointestinal distress (GI distress) can be as simple is a side ache (stitch) when running. GI distress is often caused following consumption of a food or drink and which it's effects often intensified with exercise. GI distress has a very high prevalence rate in endurance sport and is the leading cause of withdrawal from competitions. Studies vary on the number of athletes that experience GI distress great enough to cause race withdrawal, but most find high numbers of people suffering some form of GI distress either during or post event. What are the symptoms? Well it can be divided into three categories: Mechanical, Physiological and Nutritional as shown in the diagram below.
Mechanical Causes
Mechanical causes of GI distress are usually impact related from running or posture related when cycling. Bladder tears can occur in marathon and ultra runners from the repetitive bouncing of organs, resulting in internal bleeding to the intestinal wall and bladder. Impact related GI distress also contributes to lower GI issues such as flactulence, diarrhoea and urge to urinate. Blood is redistributed (shunted) from digestive organs to working muscles and the lungs, decreasing oxygen to gut organs which is also thought to increase the incidence of bleeding. Posture when cycling can lead to abdominal cramping because of the increased pressure on the abdomen being in an aerodynamic position.
Physiological Causes
Physiological causes of GI symptoms are caused from the decreased blood flow to the gut. As much as 80% of blood is shunted to working muscles and the lungs to meet exercise demands. Anxiety, caused by stress hormones can also cause physiological GI symptoms. There is no indication that fitness determines likelihood of physiological causes of GI distress, but it has been found that an element of gut training can help to reduce GI distress. This simply means eating and drinking foods when training to get your gut to tolerate food with a reduced blood flow.
Nutritional Causes
Nutrition is one of the greatest influences on GI distress because there are so many different ways that can cause it. Volume, dehydration, fibre, fat, protein, fructose and carbohydrate to list a few. Your nutrition in the hours and even days leading up to the event can also impact the gut. Foods like milk have been linked to increased bowel activity. 24-hours prior to your event it’s advisable that all food and drink consumed shouldn't cause any GI distress as it will compromise event performance and could lead to withdrawal.
We have all eaten food or had a drink of something and immediately started belching. Soda is a good example. Even worse, some foods or drinks can cause you to become flactulent such as milk or cheese. The food and drink we consume, the volume and the timing all impact digestion and can potentially result in GI distress.
Symptoms of GI distress can be very varied, but can be further seperated into 'upper', 'lower' and 'other' (see diagram to the right).
If you are eating before a training session or race, it is advised that moderate to large (8 - 12 g.kg-1.day-1) carbohydrate meals are consumed 2-3 hours prior to the session or race. It is also avisable to ensure you are adequatly hydrated. In the 2-3 hours pre event/session intake 500 ml - 1000 ml of fluid. Isotonic fluids (6 - 8% concentration) can also be used to hydrate.
As mentioned, many people suffer symptoms of GI distress following the consumption of dairy, mainly in the form of cheese and milk. It’s the same with foods very high in carbohydrate, specifically high in glycemic sugars such as malodextrin and glucose. Leading sports nutritionist and sport scientist: Asker Jekendrup recommends avoiding dairy, specifically milk the day prior to an event. Lactose being the main culprit of GI distress.
It is important to pay attention to how you feel after eating. If you are having any symptoms of GI distress, maybe it’s time to consider whether it is worth eating a particular food or an amount of somthing. Test foods out in training so that on race day you know what works for you. That means having a trial run of the 24-48 hours prior to the event, not just the meal 2-3 hours before.
