The Top 5 Reasons Why You Experience Nausea After Running

Stomach troubles and indigestion are common complaints among runners. In fact, the frequency of gastrointestinal symptoms and complaints are nearly twice as high for running than for other endurance sports, including swimming and cycling. While most of us are aware of the impact running has on our joints, our abdominal muscles also go through a lot of wear and tear with running’s up and down motion, altered motility, and endocrine secretions.

Physical exercise is both beneficial for and harmful to the gastrointestinal tract. Research shows that moderate intensity exercise plays a protective role against several serious health conditions, like colon cancer, diverticular disease, and constipation. On the flip side, acute strenuous exercise is also associated with low-grade inflammation, nausea, vomiting, stomach pain, diarrhea, and heartburn. Nearly 25 to 50 percent of elite athletes may experience gastrointestinal symptoms that can hinder them from optimal training and competitive events.

So, how can you balance the pros and cons?

Stomach Ache After Running? Here’s How to Get Past It

While there are several reasons you may experience nausea after running, making some training and lifestyle modifications can help ease the symptoms. Let’s review some of the common reasons stomach upset happens in the first place.

You Could Be Dehydrated

Strenuous exercise and dehydration are the most common causes of gastrointestinal symptoms, according to a review published in the Current Opinion in Clinical Nutrition and Metabolic Care. “This could be during or if someone goes into a run or workout underfueled or underhydrated with fluids and electrolytes,” says registered sports dietitian Kylee Van Horn.

Losing more than 2% of our body weight during exercise can have a detrimental effect on the body, such as a slowed delivery of nutrients and oxygen to cells, altered body temperature, muscle cramping, decreased cognitive function, and more—all of which can affect gastrointestinal symptoms.

Drinking enough water before, during, and after exercise, and ingesting sufficient electrolytes, can aid in fluid balance, therefore taking some of the stress off your GI system. Ensuring adequate intake of salt and electrolytes is crucial, as being low in electrolytes and salt may also result in nausea.

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Your Nutrition Timing Is Off

As runners, we know that the majority of our diets should consist of carbohydrates. Nutrient timing is a very important part of optimal GI health, especially during exercise. During a run, our blood is diverted away from the stomach, where it usually goes for digestion. Instead, the blood flows to the working muscles, so any food that’s already in the stomach doesn’t get digested as quickly.

That said, while fiber and fat are great nutrients for satiety, consuming too much of them before a run could be problematic and lead to gut dysfunction. Since fiber is not digestible, it passes through the intestinal tract undigested, which can result in gas production or cramping. Fat takes a longer time to break down in our stomachs and can lead to feelings of sluggishness, bloating, and discomfort.

Stick to low-fiber foods and predominantly carbohydrate-based foods before a run, and aim to eat larger meals two to three hours before a run to allow your body time to digest. Many people see success when they eliminate high-fiber foods days before a longer run or race.

Nausea After Running Could Signal that You’re Eating Too Much Sugar

While sports gels and drinks can be a great way to replenish carbohydrates and electrolytes mid-run, they can also cause GI issues. Because these are high in sugar, they pass through the GI system quickly so your body can absorb them faster.

A good rule of thumb is to practice training your gut beforehand with different carbohydrate-based products to see what you tolerate best.

Sometimes, Caffeine Is the Culprit

While some research suggests that caffeine can be a performance enhancer, it can also lead to an upset stomach or nausea after running. Your morning cup of coffee could do more harm than good in stimulating and irritating your stomach lining, since coffee is quickly absorbed. Caffeine can also cause feelings of anxiety and jitters in some people.

RELATED: Should You Drink Coffee Before Running or Wait Until After?

Consider swapping that caffeinated cup out for decaf, or allow more time after drinking it before your run. Keep a journal to see if your afternoon or evening runs feel any different than your morning runs after having that cup of coffee.

Your Gut Health Could Be the Problem

Probiotics may lower the incidence of GI symptoms, as well as reduce inflammation and the body’s response to oxidative damage. Furthermore, they may also improve endurance performance as gastrointestinal health is important for regulating adaptation to exercise. In a 2011 double-blind, randomized controlled trial, competitive cyclists who supplemented with lactobacillus (a bacteria found in many dietary supplements) saw reduced severity in gastrointestinal symptoms compared to those who took a placebo.

There does seem to be modest benefits to including probiotics for performance, but there’s certainly a need for additional research in this area. Either way, try including some probiotic-rich foods (such as cultured dairy and non-dairy yogurts, kimchi, sauerkraut, kombucha, or Jerusalem artichokes) in your diet to see if that helps with digestion and GI symptoms.

There is a reason why you experience nausea after running. If you make some of these changes and still suffer from gastrointestinal distress, consider reaching out to your doctor or a GI specialist to make sure you’re not facing any other underlying health issues. A registered dietitian can also help by looking at your weekly nutrition, pre-workout and during-workout nutrition, and when symptoms are present, says Van Horn. “Once the thorough examination is done, then they can evaluate holes in the pattern that could be contributing to the GI distress,” she says.