A recent collaboration with Sports Dietitian Australia ReFuel (Autumn 2021).

You’re at the starting line. Your hearts racing, palms sweating, breathes cycling and arms and legs fidgeting. Your adrenaline is spiking and your arousal is peaking, all in preparation for what lies in front. But at the same time, you’re telling yourself to keep calm, control that breath, visualise those first steps… and boom, you need to go to the toilet. ASAP! It’s game day, and once again, that nervous gut of yours is putting the brakes on your pace.

The physiology of a nervous gut

Your gastrointestinal intestinal (GI) tract is an organ responsible for digestion, absorption and excretion of matter. It is controlled via three distinct centres: (1) Myogenic control – the intrinsic rhythm of your GI muscles; (2) Hormonal control – various hormones, including cholecystokinin, gastrin and secretin, that trigger numerous functions; (3) Neural control – including your GI’s enteric nervous system (ENS) and autonomic nervous system (ANS). All of these processes work together to achieve normal GI functioning, including motility, secretion, digestion and absorption. When you see or smell food, or when food enters your gut and stimulates mechanical and chemical receptors, this triggers your central nervous system to communicate with your ENS. Your ENS is a mesh-like system of neurons that coordinates your gut functions, such as GI muscle contractions (peristalsis) plus neurotransmitter signalling. Your ANS is the second major neural controller of your GI tract. It is comprised of the parasympathetic (PS) and sympathetic systems (SS). Basically, the PS exerts its effects via the vagus nerve (innervates your oesophagus, stomach, pancreas, upper large intestine) and pelvic nerves (innervates your lower large intestine, rectum and anus). For example, when food enters your mouth, your vagus nerve stimulates muscles in your oesophagus to swallow. On the other hand, your SS coordinates your smooth muscle cells, secretory cells and endocrine cells. The ANS also regulates your breathing, heart rate, blood pressure and body temperature. On a broader level, your SS system triggers your primal “fight or flight” response, and your PS manages your “rest and digest”.

GBA and competition nerves

Your gut and brain continuously talk via nerve signals, hormones and neurotransmitters. This is referred to as the gut-brain axis and helps to explain the link between stress and gut symptoms.

When you become stressed or nervous, your “fight or flight” response is triggered, in turn diverting your body functions and energy to facing the perceived stressor. Consequently, your heart rate and blood pressure increase, your blood pools away from your GI tract to periphery muscles, heart and lungs and stress hormones (e.g. adrenaline) are released. In addition, usual body functions are de-prioritised; for instance, your digestion often slows or stops, which can result in abdominal discomfort, cramping, diarrhoea or bladder urgency. There is also increasing evidence that your GI tract responds to stress by releasing hormones such as GABA; involved in GI disturbances and anxiety. In addition, an excessive release of stress hormones can cause lipopolysaccharides translocation outside of the GI tract triggering immune and inflammatory responses often resulting in increased intestinal permeability. The physical load of exercise also induces the stress response. For instance, as exercise intensity increases there are proportional increases in stress hormones. Further to this, up to 20% of people suffer from IBS, characterised by visceral hypersensitivity; meaning their gut nerves are super sensitive to stimuli, such as gas production from high FODMAP foods.

Tips that may help manage frequent toilet trips

Pre and during competition nutrition:

  • Timing: Avoid eating your main meal for 2-4 hours pre competition

  • Avoid high fat, high fibre and high FODMAP foods

  • Low-fibre carbohydrate foods include white rice, white potato, instant oats, cornflakes and white bread.

  • High FODMAP foods to avoid include fruit juice, stone fruits, dried fruits, cow’s milk, and high fructose gels.

  • Maintain hydration: always start exercise well hydrated, choose water and low concentration drinks such as standard sports drinks (4-8% carbs). Avoid high concentration/high fructose drinks such as soft drinks, juices and energy drinks.

  • Practise mindfulness and breathing exercises to calm your GBA.