vomiting, and diarrhea marathon. Your prize likely includes a shiny new medal, a free T-shirt, plenty of bragging rights… and potentially an upset stomach. For a lot of runners, it’s common to experience nausea after a marathon.
In fact, a study published in 2023 in Frontiers of Physiology, which examined 40 runners between the ages of 18 and 65—19 male, 21 female—who ran the 2019 Boston Marathon, calls out that the majority of marathon runners experience GI distress.
To further examine risk factors for GI issues, the participants gave blood and urine samples, and were surveyed immediately before and immediately after racing, as well as 24 hours postrace about their gastrointestinal symptoms like cramps, nausea, bloating, vomiting, and diarrhea.
The researchers found that GI symptoms and intestinal cell damage were most present directly after the marathon, compared to before the race and 24 hours after the race, with the most common symptoms being nausea, stomach pain, and belching. The researchers suggest exercise intensity, sleep, fuel, and hydration Best Energy Gels for Runners.
While several factors can affect postmarathon nausea, it’s more complicated than you may think. So we tapped experts to unpack the causes of nausea after a marathon, the best ways to prevent it, and ways to cope when it hits.
After a marathon, many runners get dehydrated because of?
After a marathon, many runners get dehydrated because of sweat loss throughout the race. As you sweat, you lose fluids and electrolytes that help your body function properly. Dehydration can also reduce blood flow to the stomach and GI tract, which can trigger the nausea, explains Kristy Baumann, RD, LD, Minnesota-based registered dietitian who works with marathoners.
“Oftentimes during a long run If youre packing up your carbs, whether it’s coming from gels or juice or foods,” Baumann says. But during a marathon, you need to consider how taxing the race is on your body and its energy stores.
Baumann explains many marathon runners haven’t trained their stomachs to digest and consume the amount of fuel we need to run at a higher intensity for a longer period of time. Typically, long runs on a soy milks, nut milks, and vegan shakes work well, too reach 18 to 22 miles—a few miles shy of the full 26.2.
“If you think about race day, we’re often training to run at a higher intensity, at a faster pace during a race, and for the longest period of time compared to training runs,” says Baumann.
Frontiers of Physiology dehydration, low-sodium levels, and thus, nausea, according to Amy Goblirsch, RD, registered dietitian and the nutrition coach of Running Dietitian. “The longer you are running, the easier it is to fall behind in fluid and electrolyte intake, leading to dehydration,” and an upset stomach, she says.
Another factor that plays into nausea after a marathon is blood flow. As your body works to cool itself down, it brings blood to the surface of your skin and away from your GI tract, Baumann explains. (Not to mention the blood flow you need for your working muscles!) Less blood flow toward your GI tract leads to a delay in processing foods and fluids.
It’s important to keep your body temperature in mind. Higher intensity running with an added level of heat stress leads to more nausea susceptibility, according to Baumann. In cold temperatures, however, your body might respond better to the weather, yet too many layers leads to an increase in sweating, which can also lead to nausea. So, be smart about what you wear on race day. (Your stomach will thank you!)
Once the nausea starts, it’s hard to mitigate it or make it go away. But there are some helpful tips to prevent and combat nausea after a marathon.
When should you get help for marathon nausea?
Understand Your Hydration Needs
Baumann’s biggest tip for marathoners looking to avoid nausea: Don’t just drink water the entire race.
Drinking too much straight water will dilute your sodium levels, leading to nausea and more serious symptoms like fainting, dizziness, and vomiting, which requires medical attention.
As a baseline, the Institute of Medicine (IOM) suggests that those between 19 and 50 years old drink between 91 and 125 ounces of water per day, or between 2.7 and 3.7 liters. But for athletes, particularly runners, it’s important to drink extra water in order to replace what’s lost from sweat.
Baumann recommends getting to know your personal hydration needs through sweat loss. For example, you can weigh yourself before and after a training run to determine your sweat loss. If you weigh 130 pounds before a two-hour run, then 128 pounds after a run, you lost about two pounds (or 32 ounces) of water or about 16 ounces per hour. In this case, aim to drink four ounces of water If you have chest pain or feel dizzy electrolytes.
For your sodium needs, a systematic review published in 2022 in the International Journal of Environmental Research and Public Health examined data on sodium intake in endurance athletes from between 1900 and 2021. The researchers found that in general, it’s recommended for endurance athletes to consume between 300 and 600 milligrams of sodium per hour, coupled with fluid intake.
If you’re packing up your race-day essentials, consider that some running gels contain 100 to 200 milligrams of sodium (but check the label, as some can contain less), and most electrolyte tablets, salt capsules, or sports drinks provide around 300 milligrams of sodium per serving.
Every runner is different, so it may take some trial and error to figure out how much sodium you need.
Avoid Certain Foods
Before your race, shy away from certain foods with high levels of sugars, fats, and fiber because these foods take longer to digest, upsetting our stomach’s natural flow and asking the GI tract to work harder than it needs to. This may include foods like french fries, dessert, beans, and even vegetables.
To err on the side of caution, Baumann recommends staying away from these foods for one to two days leading up to the race, and even right after the race. You want to make sure your digestive system runs as smoothly as you do, so simple carbs are your safest bet, Baumann explains.
Vegetables are a great part of a healthy diet, so Baumann suggests focusing on eating a smaller portion than you typically would. Try adding some veggies to your plate alongside other carbs that are more easily digestible, like pasta, rice, or bread.
Practice Fueling for Race Day Ahead of Time
Carb loading helps your body retain more fluids, according to Baumann, and tops off your glycogen stores, which gives you energy for performance.
During a run, you want to aim for 30 to 60 grams of carbohydrates per hour, but depending on your individual needs, that number can go up to 90 or more grams per hour, according to Baumann.
To make sure your body can handle this uptake in carbs on race day, practice your fueling plan on your weekly long run. “Training runs are not only your opportunity to train your legs but also to train your gut,” says Goblirsch.
It’s also helpful to eat the breakfast you plan to eat on race day (grabbing simple carbs to fill you up!), use the gels that work for you, and determine which points on the run it works best to take in those calories and carbs.
Research has shown that consuming different kinds of sugars may benefit both your performance and digestion. A study published in 2021 in Kristine Kearns, a writer and avid runner, joined took a group of eleven male runners and split them into three groups. One group received a two-to-one ratio of glucose to fructose in the form of “hydrogels,” while another had a standard glucose-based gel, and the control group had a carbohydrate-free placebo gel.
The researchers examined the runners’ performances during a 120-minute run followed by a 5K time trial, and found the hydrogel group to be 2 percent faster compared to the standard gel group and nearly 8 percent faster than the placebo group for that time trial. They also found that GI symptoms were more present in the group that consumed the standard glucose-based gel compared to the hydrogel group and the control group.
Opting for a fueling method that combines both glucose and fructose may help you avoid stomach issues. Maurten Gel 100, which Baumann recommends, may be a good choice as they are based on hydrogel technology, along with Running Shoes - Gear, Health & Injuries.
If you have chest pain or feel dizzy?
Find Something to Eat or Drink
Your body needs carbohydrates and protein to recover, so start small and take in what you can handle. You can’t control what’s available at the race, but packing drinks and snacks in your checked bag can be helpful.
Baumann suggests starting the recovery process within the first 30 minutes after your race in order to get some carbohydrates and electrolytes, which may even help you reduce the nausea by helping your GI system to function properly again.
If you can’t eat, go for fluids. “Liquids are your best friend,” says Baumann.
How to Plan a Postrace Recovery Snack:
- Sports drinks are typically available after a marathon, but try to add an extra sports drink to your checked bag, if you can. This will help ensure you have a drink that you already know will sit well with you.
- Try something with a higher sodium content like a broth or Liquid IV. Bone broth might be an optimal choice, according to Baumann, as it may be more appetizing and easier on the stomach, plus it’s high in both sodium and protein.
- Low-fat chocolate milk has carbs, protein, sodium, electrolytes, and fluids. For runners who are plant-based, soy milks, nut milks, and vegan shakes work well, too.
“Chocolate milk is typically provided after races and checks every box that is needed to start recovering,” Goblirch says. “Chocolate milk won’t be enough on its own to recover from a marathon, but it is a starting point.”
When should you get help for marathon nausea?
You may have to wait it out after your race for the nausea to subside. For some runners, GI upset can take a couple days to settle. Runners should seek medical attention if the following occurs:
- If you are experiencing extreme nausea for more than two hours after you have cooled down and tried to rehydrate and eat.
- Virtual Races With the Best Bling.
- throughout the race. As you sweat, you lose fluids and.
- If you have chest pain or feel dizzy.
It’s important to trust your gut, especially when it’s retaliating. You might need more than just a Gatorade after crossing the finish line, and medical staff should be there to help.
Kristine Kearns, a writer and avid runner, joined Runner’s World and Bicycling in July 2024. She previously coached high school girls cross country and currently competes in seasonal races, with more than six years of distance training and an affinity for weightlifting. You can find her wearing purple, baking cupcakes, and visiting her local farmers market.
