Strenuous exercise can cause significant GI symptoms

Last Updated: 2017-06-20

By Will Boggs MD

NEW YORK (Reuters Health) - Strenuous exercise can result in gastrointestinal injury and symptoms, according to the authors of a systematic review.

"Moderate to vigorous exercise over two hours has consistently been shown to significantly damage the gut and is associated with increased incidence and severity of gastrointestinal symptoms,” Dr. Ricardo J. S. Costa from Monash University, Notting Hill, Victoria, Australia told Reuters Health by email.

Exercise, while beneficial for prevention and management of various diseases, can be associated with exercise-induced gastrointestinal syndrome, which refers to disturbances of gastrointestinal integrity and function.

When Dr. Costa and colleagues analyzed data from healthy populations and patients with chronic gastrointestinal conditions, they found that increased exercise intensity and duration are associated with increases in measures of intestinal injury, permeability, and endotoxemia, as well as impairment of gastric emptying, slowing of small intestinal transit, and malabsorption.

All these markers of gastrointestinal disturbance can be exacerbated by the addition of heat stress and particularly during running, they noted online June 7th in Alimentary Pharmacology and Therapeutics.

It is unclear from the literature whether individuals with gastrointestinal conditions have a greater incidence or severity of exercise-induced gastrointestinal syndrome compared with healthy counterparts, they add. Furthermore, there has been no research on the prevention and management of exercise-induced gastrointestinal syndrome in patients with these conditions.

What is clear is that gastrointestinal symptoms developing during exercise invariably resolve, the authors emphasize.

For prevention, they recommend starting exercise hydrated and maintaining hydration throughout, optimizing carbohydrate consumption during exercise, and avoiding nonsteroidal anti-inflammatory drugs (NSAIDs) before exercise.

A low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet might also be beneficial, but blinded studies have not found a gluten-free diet to be beneficial in non-celiac athletes.

“If athletes present with exercise-associated gastrointestinal symptoms, it is important to refer for a gut assessment during exercise to establish the individual causal mechanism of exercise-induced gastrointestinal syndrome,” Dr. Costa said.

His advice: “Participate in exercise within individual comfort zone and allow sufficient recovery time between sessions.”

Dr. Tanja Oosthuyse from University of Witwatersrand Medical School, Johannesburg, South Africa, who has published extensively on exercise and its effects, emailed to Reuters Health her advice for athletes who want to reduce the risk of GI symptoms.

-Ensure the last meal is ingested at least 2 h before exercise.

-Ensure carbohydrate supplement beverages are not too concentrated, i.e., not greater than 8% carbohydrate (CHO) solution.

-Maintain euhydration during exercise and include electrolytes to prevent hyponatremia.

-In hot conditions, when splanchnic blood flow may be restricted, reduce carbohydrate intake slightly.

-Use cooling strategies, such as ingesting sports drinks with crushed ice and frequently cooling the neck and head, to help reduce the central perception of thermal stress and possibly lessen the restriction on splanchnic blood flow.

-Avoid ingesting low glycemic index carbohydrates during exercise because they have increased intestinal retention time and cause increased intestinal fluid retention resulting in severe GI symptoms.

-Regular ingestion of CHO supplements during training will upregulate intestinal CHO transport and absorption pathways.

-Never ingest NSAIDS during prolonged exercise.

-Carefully regulate exercise intensity during prolonged exercise sessions to ensure that the proportion of time exercising at a high intensity above lactate threshold is controlled (less than 10% of exercise time in very long exercise bouts).

-Runners with frequent GI symptoms should consider cross training with cycling to reduce episodes of intestinal injury.

SOURCE: http://bit.ly/2rqF2RE

Aliment Pharmacol Ther 2017.