There’s a reason that American Olympian Bill Rodgers stated that “more marathons are won or lost at the porta-toilets than at the dinner table.” Many athletes suffer from gut issues around an event (an estimated 30-90%), and there are multiple reasons for this, like physiological changes during exercise, stress, and heat (3).
What are the causes?
Blood flow is redirected away from major organs and towards muscles during vigorous exercise, which affects gut function. Anxiety is heightened before a big event, which can trigger symptoms or cause them to worsen. When events are held in high temperatures sweating can cause dehydration, which complicates things even further. Vigorous physical movement can also conspire to create the perfect storm. The contorted posture that cyclists and many triathletes maintain for extended periods puts pressure on the intestines and creates an urgency to get to the nearest bathroom (2).
If you’re an endurance athlete who also suffers from digestive issues due to irritable bowel syndrome (IBS) or irritable bowel disease (IBD) in addition to the commonly-experienced GI issues for athletes, you know how difficult those symptoms can be to manage. Whether they are an occasional intrusion or a persistent obstacle, suffering from symptoms like diarrhea, bloating, or stomach pain while training is completely incompatible with your ability to perform your best as an athlete. For many athletes, it can be helpful to manage symptoms by following the low FODMAP diet to avoid potential upsets (1).
Low FODMAP; Why is it so tricky?
As an elimination diet that avoids many carbohydrates and sugar alcohols found in numerous foods, the low FODMAP diet can be challenging for anyone, but particularly for athletes who need to fuel with meals and snacks that are full of nutrition and high calorie before, during, and after training. It can be tricky to know how to juggle getting enough calories, eating the right foods at the right times, and not triggering symptoms. Fortunately, with the right approach, and a little planning, things can feel more manageable and less like a tightrope walk.
In general, high-fiber foods should be avoided on the day of an event, even amongst acceptable elements within the low FODMAP diet. While it’s important to have enough fiber in your diet while training, it should be consumed sparingly or avoided on event day due to the possibility of causing gastrointestinal distress (2).
Sugar alcohols, beans/ legumes, and lactose can be major FODMAP offenders for many people, and tricky for many athletes with stomach troubles to handle near a big event, with or without IBS or IBD. Many vegetables and fruits such as apples, pears, onions, garlic, stone fruits, cauliflower, and others are high in FODMAPs. Some of these may be tolerated by some people and not others, which should be discovered in the reintroduction phase of the diet (4).
One of the largest hurdles for athletes is that many nutrient-packed, whole grain carbohydrates that could typically be used to fuel up or “carb load”, are not included in the low FODMAP diet due to high FODMAP content. Eating bowls of wheat-based pasta leading up to a big race won’t exactly cut it if it can also lead to bouts of explosive diarrhea. However, there are many low FODMAP options to use as carbohydrate alternatives that are high in nutrition, such as gluten-free bread and pasta, rice, quinoa, baked potatoes, or oats, which are all carbs that should be easy on your digestive system (4). You can find a cohesive list of what foods are acceptable and what foods to avoid on the low FODMAP diet here.
What else can I do to make things go more smoothly?
Because it can be challenging to manage which foods are acceptable and in what portions, it may be helpful to work with a Registered Dietitian (RD) who is also trained in sports nutrition. This could be especially helpful as you move through the three phases of the elimination diet, from elimination to the reintroduction of possible triggers, to personalization. An RD can also help you decide if you should be on the diet long term, going through all three phases of the elimination diet, or not. If you’re a mostly healthy athlete with limited GI issues, a shorter-term approach to low FODMAP, in the days leading up to an event, might be enough for you (2).
It’s important to note that for the average athlete with tummy issues, the low FODMAP diet should be temporary. This means that after about four weeks or so, you can begin reintroducing items back into your diet individually to see which ones have been ailing you, and which ones don’t seem to be harming you. It’s always preferable to get as much nutrient diversity as possible, which is why this phase is important (4).
A bit of sage wisdom that holds true is to avoid making any major changes before a big event or race -- which includes nutrition. If you are in the reintroduction phase of the low FODMAP diet, any new introduction should be eased into in the weeks leading up to an event and not started abruptly before an event to avoid any sudden shock to the system or adverse effect. It’s also important to experiment with pre-game meals many times beforehand so as not to encounter any surprises on the actual day of an athletic event (2).
Whether you decide to work with a Registered Dietitian or figure things out on your own, tackling a low FODMAP diet while endurance training can be manageable. By choosing your foods thoughtfully and your carbs wisely, avoiding sudden nutrition changes or possible triggers before a race, as well as doing other basic things not related to your FODMAP diet (like getting enough sleep, plenty of hydration, and avoiding too much stress), you can increase the odds that your stomach troubles will be kept at bay.
Dana M. Lis, “Exit Gluten-Free and Enter Low FODMAPs: A Novel Dietary Strategy to Reduce Gastrointestinal Symptoms in Athletes,” National Center for Biotechnology Information, Sports Med, 49(suppl. 1): 89-97, published online January 22, 2019, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6445805/
Erick Prado de Oliveira, et. al., “Gastrointestinal Complaints During Excercise: Prevalence, Etiology, and Nutritional Recommendations,” National Center for Biotechnology Information, Sports Med, 44(suppl. 1): 79-85, published online May 3, 2014, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4008808/.
Jill Barker, “Runners are Prone to Tummy Trouble,” Pressreader, Montreal Gazette, published online July 7, 2014, https://www.pressreader.com/canada/montreal-gazette/20140707/281517929223673.
Mara Santilli, “Should Athletes Follow a Low FODMAP Diet?,” Unbreakable Nutrition, Spartan Race, accessed July 19, 2021, https://www.spartan.com/blogs/unbreakable-nutrition/low-fodmap-diet.