Runner's Diarrhea: Causes and Prevention

Runner's diarrhea is a problem that affects most marathon runners. Fortunately, there are several things you can do to prevent it, as we'll explain in this article.
Runner's Diarrhea: Causes and Prevention

Last update: 28 July, 2020

Long-distance and marathon runners are all too familiar with runner’s diarrhea. While it might be difficult to believe, this is a common problem and a recognized issue within the world of sports medicine.

Broadly speaking, runner’s diarrhea comes with all the symptoms associated with typical diarrhea, with more frequent bowel movements, and looser stools. As a general rule, up to three trips to the bathroom a day is considered normal.

That said, fear of provoking runner’s diarrhea shouldn’t stop you from playing sports or doing physical exercise. In fact, practicing sports is highly recommended for anyone who frequently experiences digestive issues, as it can help to regulate peristalsis. What’s more, aerobic exercise can also help our bodies to relax, reducing gastrointestinal bleeding and symptoms associated with gastric ulcers.

Causes of runner’s diarrhea

Runners who experience exercise-related diarrhea often struggle to identify the underlying cause. This can be confusing, leading them to try out multiple different treatments, which often have little to no effect.

One of the main causes of runner’s diarrhea is anxiety. This becomes particularly obvious in the case of elite athletes who compete at a more demanding level. Diarrhea may start to appear days before, or even on the morning of an important competition.

The best way to treat cases of anxiety-related diarrhea is to consult a therapist. If you allow your anxiety to go unchecked, you’ll continue to have gastrointestinal issues.

Stomach pain.

Another common cause is the physical jostling of the intestines during running. This can actually change the permeability of the intestines so that they absorb less ingested food. This, in turn, leads to looser stools, and an increase in the number of bowel movements.

The athlete’s diet will also determine whether or not they experience runner’s diarrhea. For example, some athletes may ingest large amounts of fiber in order to control their weight. However, this can actually cause excessive peristalsis.

On the other hand, calorie gels can also be a big issue. These are often used to provide a quick burst of energy in the middle of a competition. It’s important to be aware, however, that some formulas have a high glucose content that our intestines can’t always handle.

Runner’s diarrhea

Luckily, there are some steps you can take to prevent runner’s diarrhea. These are just some basic guidelines that every athlete can follow. It’s simply a matter of incorporating good habits and making them a part of your training routine.

Our first recommendation is to regulate the amount of fiber in your diet and opt for foods that don’t cause gas. If you’re going to ingest large amounts of dietary fiber, it’s best to wait until after your daily training session.

Caffeine is a substance that can stimulate peristalsis, so it’s best to avoid drinking coffee until six hours before your race. The same applies to any foods which contain sorbitol – such as sweets or some sugary cookies – as well as any dietary supplements that contain it.

Moreover, because dehydration is closely associated with intestinal permeability, it’s important to stay hydrated. Runner’s diarrhea can result in an electrolyte disorder, leading to hyponatremia and collapse.

It’s also important to note that anti-inflammatory drugs should never be taken without a prescription. This is especially true of non-steroidal anti-inflammatories, which are known to cause gastrointestinal issues. For joint or muscle pain, a small dose of paracetamol is best, although you should always consult with a doctor first.

Prevention and nutrition

In addition to devising a diet plan that meets your caloric needs and suits your individual digestive system, there’s one supplement you may want to include: the prebiotic. This is really easy to do and will help protect the lining of your intestines.

Prebiotic foods can help prevent runner's diarrhea.

Prebiotics, found in food such as garlic, onion, leeks, and other types of fruit and veg, provide natural bacteria that often live in our digestive systems. This bacterial flora is a powerful defense against diarrhea.

Along with the use of prebiotics, we’ll re-emphasize the importance of regulating your intake of dietary fiber. For an athlete, around 1 oz of fiber, a day is more than enough. However, people often tend to increase the quantity of fiber in their diet in an effort to lose weight before a race.

If you decide to try to lose a few pounds before a competition, changes to your diet cannot be made lightly. It’s always best to consult with a health professional who specializes in sports nutrition.

Runner’s diarrhea is preventable

In short, while runner’s diarrhea isn’t a serious condition, it can be very uncomfortable. If running is something you enjoy, suffering from this kind of diarrhea may even stop you from doing something you enjoy. If this is you, it’s important to focus on finding ways to prevent it, so we hope you’ve found the tips and advice in this article useful!

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