Strenuous exercise may induce acute but reversible disturbances in gastrointestinal health
Strenuous exercise appears to exert a negative, albeit reversible, impact on gastrointestinal integrity and function, according to a team of Australia-based researchers. The extent of the said gastrointestinal changes may increase further depending on the intensity and duration of exercise.
In a systematic review, researchers identified relevant studies reporting on the impact of acute exercise on several markers of gastrointestinal integrity and function and found considerable evidence for increases in indices of intestinal injury, permeability and endotoxaemia, together with malabsorption, gastric emptying impairment and small intestinal transit slowdown. [Aliment Pharmacol Ther 2017;46:246–265]
Several field-based observational studies comprehensively assessing gastrointestinal symptoms during extreme endurance events reported a particularly high incidence and severity of symptoms in both the upper (eg, regurgitation, upper abdominal bloating, belching, epigastric pain, heartburn) and lower (eg, flatulence, urge to defecate, lower abdominal bloating, abdominal pain, abnormal defecation) gastrointestinal tract.
The said symptoms limited performance of prolonged strenuous exercise, resulting in withdrawal from competition due to their severity and to more worrying clinical features, such as acute colitis including faecal blood loss, in certain cases.
Factors that were identified to promote exacerbations or development of gastrointestinal disturbances included hot ambient conditions (≥30°C), running mode and female gender. Irrespective of fitness level, significant gastrointestinal perturbations occurred at an exercise stress threshold of ≥2 hours at 60 percent of the maximum oxygen consumption (VO2 max).
“Exercise-induced gastrointestinal syndrome has the ability to create acute disturbances in the health of the gastrointestinal tract due to multiple physiological changes associated with hypoperfusion and ischaemia, epithelial injury, impaired barrier function, impaired nutrient absorption, altered gastric and intestinal motility, endotoxaemia, local and systemic inflammation,” they explained.
They pointed out that the components of exercise-induced gastrointestinal syndrome may have adverse health implications for patients with chronic gastrointestinal diseases already associated with compromised gastrointestinal integrity and function, specifically patients with inflammatory bowel disease or functional gastrointestinal disorders including irritable bowel syndrome and functional dyspepsia.
Adverse effects of strenuous exercise to especially watch out for are as follows: (1) repetitive injury to the intestinal epithelium with insufficient recovery time in-between insults; (2) effects on gut motility associated with intestinal hypoperfusion, ischaemia and altered enteric nervous activity during exercise; and (3) local and systemic inflammatory responses related to intestinal injury enhanced epithelial permeability, endotoxaemia and the oxidative stress associated with reperfusion. [World J Gastroenterol 2016;22:2760-2770; Biochim Biophys Acta 2009;1788:864-871; J Gastroenterol 2014;49:375-387]
While there is evidence for health benefits of moderate exercise in patients with inflammatory bowel disease (IBD) or functional gastrointestinal disorders (FGID), the issue of whether strenuous exercise can induce or precipitate IBD or FGID in previously healthy individuals is unclear and requires further investigation, researchers said.
Meanwhile, there are several strategies that can be adopted to prevent or reduce the severity of exercise-associated gastrointestinal perturbations, including maintenance of euhydration, dietary supplementation, carbohydrate consumption during exercise and avoidance of gastrointestinal irritants particularly nonsteroidal anti-inflammatory drugs.
“[Given that] exercise-induced gastrointestinal syndrome is multifactorial in origin, assessing gastrointestinal barrier integrity and functional responses during and/or after exercise in those individuals presenting symptoms … is key to establishing the potential underlying mechanism(s) and biomarkers to recognise them on an individual basis, subsequently informing and tailoring preventive and management strategies,” researchers said.