If members of the public were polled to name the most important anatomical and physiological features that make a great athlete, several answers would likely come up over and over again—powerful muscles, a big heart, efficient lungs, nerves of steel. References to the digestive tract would almost certainly fail to make it to the top of people’s lists. To be sure, all of us are aware that the gastrointestinal tract—or the gut, as I’ll also call it—breaks down and absorbs the foods we eat, but many of the other indispensable duties of this roughly 30-foot-long fleshy tube remain opaque to the average Joe or Jane.
Even though most of the public doesn’t consider the gut to be a key part of sporting success, countless athletes know all too well how crucial it can be to making the winners’ podium or even simply finishing a race, for that matter. For many, their guts have betrayed them in the midst of competition or during a critical training session. Indeed, it’s safe to assume that almost every athlete has—at some time or another—been stricken with gut distress. If you’re reading this book, it’s fair to assume you’ve experienced gut dysfunction yourself, or at least know of an athlete who has. Maybe you had to duck into roadside greenery to assuage an angry bowel. Maybe you were overcome by an excruciating side stitch that stopped you dead in your tracks. Maybe you tossed your déjeuner in the locker room because of pre-game nerves. Or perhaps you’re one of those unfortunate souls who suffers from nearly every conceivable form of digestive torment known to man. Rest assured, you’re not alone.
Although it’s difficult to generalize about the prevalence of gut distress during exercise (it depends on exercise intensity, duration, and a survey’s methods), the great majority of endurance athletes and even many team-sport athletes at least occasionally struggle with unpleasant symptoms.1, 2 Even the elite of the elite aren’t immune to these digestive disturbances. Bill Russell (Boston Celtic and 11-time NBA champion), Steve Young (San Francisco 49er and three-time Super Bowl winner), Jim Ryun (1960s running phenom), Paula Radcliffe (former world record–holding marathoner): these names represent just a smattering of notable athletes who have had encounters with severe or reoccurring gut troubles before or during competition.
This book—organized into three parts—addresses the causes of and solutions to athletes’ alimentary afflictions. In Part 1, I answer the question of why so many athletes develop unpleasant gut symptoms, particularly in the midst of their most important contests. As you’ll learn, there’s not a singular answer to this question. Instead, each symptom—whether it is nausea, reflux, flatulence, or diarrhea—often has its own unique underlying origins, and that is precisely why I take a symptom-by-symptom approach to understanding and managing gut disturbances. For example, a strategy that alleviates nausea may be of little value for managing abdominal cramps. Likewise, tips for preventing reflux may do nothing to ease urges to defecate. Further, the ideal tactic for managing a given symptom can differ depending on the situation. Take for example nausea, a vexing ailment that often rears its ugly head not only during intense exercise like sprinting, but also during extremely prolonged exercise. Although nausea may feel the same in both situations, the underlying causes do differ. Consequently, the strategies I discuss for dealing with a particular symptom often vary depending on the circumstances.
Part 2 of The Athlete’s Gut is devoted exclusively to diet-gut interactions, and it is easily the largest section of the book. This shouldn’t be surprising given that the main job of your gut is to digest and absorb the variety of victuals you consume day in, day out. I take a nutrient-by-nutrient approach to illuminate how various components of your diet can trigger—or, in some cases, relieve—gut woes. Energy, carbohydrate, fat, protein, fluid, sodium, and a variety of supplements are discussed in detail. I also review what the science says about your gut’s capacity to morph and change in response to stimuli. Simply asked, is it possible to train your gut over time to tolerate greater intakes of food and fluid during exercise? As you’ll come to find out, the evidence tells us that—just as with your muscles, lungs, and heart—your gut is a highly malleable organ that is capable of adapting to the various exposures it encounters, whether that be avocado toast or Twinkies.
There’s another reason such a sizeable chunk of The Athlete’s Gut is devoted to diet: it’s been the focus of my professional training for the past 15 years. The first five years of this journey was spent becoming a registered dietitian, which included obtaining a bachelor’s degree in dietetics and completing a nearly yearlong internship at the Mayo Clinic. Over the next five years, I obtained master of science and doctorate degrees in exercise physiology from the University of Minnesota. It was during this time that my attention shifted toward studying gut function in athletes; my PhD research evaluated the use of a carbohydrate feeding strategy in runners that was previously utilized with success in cyclists. Although I won’t go into the specifics now (they’re covered in Chapter 4), this tactic involves consuming multiple types of sugars as a way to maximize carbohydrate burning while also minimizing unpleasant bowel symptoms. For one of my studies, I spent roughly one hundred hours measuring physiological responses and gut symptoms in 20 runners who slogged away on a treadmill in two-and-a-half-hour blocks of time. After finishing my PhD in 2014 and working for a year as a postdoctoral researcher in Nebraska, I moved to Virginia to take a faculty position at Old Dominion University. During my time at Old Dominion, I’ve continued to perform studies on gut function in athletes, some of which are detailed in the pages that follow.
Telling you about the extent of my training isn’t an attempt to impress you. In reality, I have a strong aversion to talking about myself. (Perhaps it’s the aw-shucks-Minnesotan in me.) Nevertheless, it’s incumbent on me to be transparent in terms of my expertise. To use the parlance of baseball, nutrition science is most definitely in my wheelhouse. In contrast, there are some topics covered within the pages of The Athlete’s Gut that I haven’t received formal training in. Part 3 covers one of these subjects, the connections between the mind and gut dysfunction. Even though I don’t have formal psychological training to draw on, I rely extensively on the research and wisdom of scientists who have spent their careers trying to understand the connections between the gut and the brain. Still, you’ll find caveats strewn throughout The Athlete’s Gut, because, in my experience, anyone claiming to be an expert in everything while also offering simple solutions for complex problems are, to put it mildly, usually full of equine crap.
After reading Parts 1, 2, and 3 of The Athlete’s Gut, you should have a much-improved understanding of how exercise affects your gut, how your nutritional choices impact gut symptoms, and how the connections between your mind and gut contribute to digestive misfortunes. Along the way, you’ll read anecdotes of gut mishaps that have befallen prominent athletes throughout the years; these stories serve as powerful reminders that enteral problems can strike any athlete, even those in the upper echelon of their sport. Much of this book, though, is devoted to reviewing the scientific investigations that have shed light on the mysteries of the gut over the past two centuries, from a case study of a fur trapper with a fist-sized hole in his stomach to studies that employ million-dollar functional brain scanners. In fact, I rely on roughly seven hundred references, most of which come from the esoteric pages of scientific journals. As a scientist, I’ve been trained to substantiate nearly every claim I put forward, and while this makes for a laborious writing process (to the annoyance of my wife, I probably could have finished this book in half the time if I had used a less scrutinizing writing style), it allows you, the reader—if you so desire—to evaluate the veracity of my claims. This style of writing is so important today given the voluminous quantity of dubious health and performance claims found on the internet and social media.
Most of the material in this text pertains to “normal” functional changes that come about during training and competition. Obviously, millions of athletes across the world live with medical illnesses that affect the gut. While The Athlete’s Gut is mainly concerned with the changes that occur before and during exercise and competition, I would be remiss if I didn’t also review some of the ailments that directly or indirectly impact the digestive system. Likewise, medications that target gut functioning and symptoms have obvious implications for athletes. Consequently, Appendix A provides an overview of disorders that can be a source of gut problems, while Appendix B provides a summary of medications commonly used to manage gut symptoms or that are known to induce gastrointestinal side effects. One point I need to make clear is that the material covered in this book—including in Appendixes A and B—is for informational purposes and isn’t intended to diagnose, treat, or cure any gastrointestinal (or other) medical condition. I can appreciate that it’s not fun to tell someone else about problems like chronic explosive diarrhea or straining on the loo, but you should seek the counsel of a trusted healthcare provider if you’re personally suffering from persistent or bothersome gut problems.
With each passing year, we learn more about how the gut functions in response to stressors like exercise and athletic competition, and although there are questions we still don’t have the answers to, The Athlete’s Gut should serve as a go-to, science-based resource when dealing with digestive difficulties in athletes. Athletes spend countless hours training to improve their fitness and refine their skills. Some even spend thousands of dollars on the latest and greatest pieces of equipment or technology that, in many cases, end up having no lasting impact on performance. For many athletes, the alimentary canal is an afterthought, akin to the plumbing in their home in that they take it for granted until something goes horribly awry.
Marathon legend Bill Rodgers, who won a combined eight Boston and New York City Marathons, is reported to have told a group of runners that “more marathons are won or lost in the porta-toilets than at the dinner table.”1 While maybe not accurate in an absolute sense, this statement rings true for an awful lot of athletes around the world. My hope is that by reading The Athlete’s Gut you’ll gain a better grasp of the inner workings of your gut and, by applying this newfound knowledge, reduce the chances that your next contest will be ruined by a petulant bowel.