While super-short workouts are making headlines for their fitness merits, super-long workouts are catching some flack. According to a systematic review in Alimentary Pharmacology and Therapeutics, long, intense workouts may increase the risk of gastrointestinal issues. The review looked at data from controlled studies, which included both healthy people and people with gastrointestinal conditions, investigating the effects of strenuous exercise on markers of gastrointestinal injury, intestinal hyperpermeability (also known as leaky gut), endotoxemia (toxins from gut bacteria in the blood), abnormal motility, and malabsorption. Based on their review, the researchers concluded:

• In healthy people, regardless of their fitness level, markers of intestinal injury, leaky gut, and endotoxemia were significantly increased after high-intensity exercise (usually running) lasting two hours or more. In addition, malabsorption and motility disturbances were more likely after long, vigorous workouts.
• Symptoms of digestive distress, related to both the upper and lower gut, frequently occurred with long and strenuous exercise.
• Hot weather and dehydration were additional stressors that appeared to exacerbate the risk of exercise-induced gastrointestinal disturbances.
• People with gastrointestinal conditions generally experienced health benefits from moderate exercise, but the risks of strenuous exercise in this population are still unknown.

Although the long-term consequences of prolonged strenuous workouts are not known, according to this study, people who love a long run may want to keep it under two hours to avoid digestive disturbances. But, if you’re a marathon runner or a triathlete, this might not be an option for you. If that’s the case, here are some tips to keep your gut happy while you’re going the distance:

• Stay hydrated. Certain evidence shows that dehydration could impair gastric emptying and increase gastrointestinal issues, including nausea.
• Carb load during your run. Eating high-carb snacks during a prolonged exercise routine may help support several aspects of healthy gut function.
• Prepare for your run with a snack. One study found that eating a high-carb snack during training sessions reduced gut discomfort, nausea, and upper-gastrointestinal symptoms during a follow-up three-hour run.

Source: Alimentary Pharmacology and Therapeutics