Can athletes benefit by lowering the FODMAP content of their diet?

Several studies report that following a low FODMAP diet can greatly help people suffering from Irritable Bowel Syndrome (IBS) in managing their symptoms. Can the low FODMAP diet also help athletes deal with exercise-induced, IBS-like gastrointestinal symptoms?

What are FODMAPs?

FODMAPs are Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols. These poorly absorbed, short-chain carbohydrates reach our colon largely undigested and are rapidly fermented by our gut bacteria to produce gas. In addition to their inherent water-absorbing potential, the gas produced from the fermenting FODMAPs can lead to painful symptoms (1).

Consuming foods that are high in FODMAPs can cause most people to struggle digestion-wise, but in individuals with a sensitive gut, the pain and discomfort are more strongly manifested. Particularly, in patients suffering from Irritable Bowel Syndrome (IBS), bloating, flatulence, diarrhea, abdominal cramps, and constipation are common after a high FODMAP meal (1).

IBS is a functional gastrointestinal (GI) disorder characterized by abdominal pain and altered bowel habits that affects ~ 11% of the world’s population (2). Reducing FODMAP intake can prove to be greatly beneficial in these individuals (1, 3). There is an ever-increasing body of clinical evidence that shows that a diet low in FODMAPs can address abdominal symptoms in ~70% of IBS patients (4, 5). 

Do athletes experience IBS-like symptoms?

Exercise-associated physiological disturbances can affect the function and integrity of our gastrointestinal system. It is not surprising then that 30-50% of endurance athletes commonly report GI symptoms such as abdominal cramps, flatulence, urgency of bowel movements, and diarrhea (6). The lower GI symptoms reported by athletes are similar to those of IBS. A 2019 survey shows that about 10% of marathon, ultramarathon, half-distance, or full-distance triathlon athletes have actually either been diagnosed with IBS or meet the Rome III IBS diagnostic criteria (7). However, most endurance athletes who suffer from IBS are undiagnosed, while even more experience GI symptoms but do not fit the diagnostic criteria.

The occurrence of painful GI symptoms can interrupt or prevent training and thus, negatively impact athletic performance or even subsequent recovery. In fact, anecdotally, GI problems are perhaps the most common cause of underperformance in endurance events. Marathon legend, Bill Rodgers, a four-time champion in both the Boston Marathon and the New York City marathon in the late 1970s said, “More marathons are won or lost in the porta-toilets than at the dinner table”, highlighting the scale of GI ailments that occur in athletes, particularly long-distance runners.

What causes IBS-like symptoms in athletes?

Scientists aren’t 100% sure why some athletes struggle with IBS-like symptoms more than others. Experts believe that the mechanical, psychological, environmental, and nutritional components of strenuous exercise can cause athletes to experience GI issues (6, 8). From the nutritional standpoint, the FODMAP concept is particularly relevant to athletes, since carbohydrates are routinely recommended for energy, improved performance, and recovery (17). 

In fact, foods most heavily marketed towards athletes are probably the most FODMAP-rich products that exist (18). Popular wheat, barley and rye products for athletes are loaded with a particular type of FODMAPs called fructans. A closer look at the “low sugar” flavored sports drinks, gum, mints, or protein bars geared towards athletes reveals that they often contain sorbitol, mannitol, or xylitol (the P in FODMAPs) as sweeteners. 

Recently, the concept of exercise-induced GI syndrome has been introduced to describe GI symptoms associated with exercise that is strenuous in duration and intensity (8). As is true with IBS, dietary factors are hypothesized as one potential contributor to the symptoms associated with this syndrome. Thus, endurance athletes could potentially benefit from currently prescribed IBS-mitigating strategies such as the low FODMAP diet. 

Can FODMAP restriction improve GI symptoms in athletes?

Indeed, the low FODMAP diet is emerging as a novel regime thought to improve GI health and reduce the risk of exercise-associated GI symptoms (19). Although other factors contributing to GI distress are not easily modifiable during high-intensity activity characteristic of endurance training, athletes can try to manage their dietary FODMAP intake. It appears that many athletes may already be altering their diets to eliminate some high FODMAP-containing foods to reduce GI distress without intentionally restricting FODMAPs (9).

A low FODMAP diet typically begins with a 4 - 8 week elimination period, which completely removes or restricts foods high in FODMAPs. When the symptoms begin to alleviate, foods high in FODMAPs are re-introduced one by one into the diet to identify the type and amount of tolerable FODMAPs. A Journal of the International Society of Sports Nutrition study shows evidence that a low-FODMAP meal plan can improve symptoms of endurance exercise-related IBS, and may give athletes the ability to train for longer periods of time as a result (10). More case studies and interventions have further supported the potential for a low-FODMAP diet in athlete GI symptom management (11-14). The low-FODMAP diet was listed as a successful strategy for mitigating exercise-induced GI symptoms in a very recent study published in Frontiers in Nutrition (15). Thus, guided by a qualified sports nutrition practitioner, FODMAP restriction may be an effective strategy to reduce the magnitude of exercise-associated IBS-like symptoms.

Is there an alternative to the low FODMAP diet approach?

For some athletes, trigger foods may only elicit symptoms when ingested before or during strenuous exercise. In such cases, reduction of these foods might only be required 1–3 days before and during intensive endurance exercise (20). However, if the long-term low FODMAP diet is recommended then the three phases of the diet, as designed by the gastroenterology researchers at Monash University, should be followed.

Unfortunately, getting optimal nutrition to fuel intense activity might be challenging while adhering to the restrictions of the low FODMAP diet (20). Long-term adherence to the low FODMAP diet can also lead to a lower intake of dietary fiber, reduced nutrient diversity, and alterations in gut microbiota - all of which can affect overall gut health (21). Inherently, the low FODMAP diet is not designed to be followed long-term due to possible nutritional deficiencies. The potential for unnecessary food restriction leading to eating disorders is also a key consideration.

Another important hurdle to the successful application of the low FODMAP diet is the scarcity of information defining the FODMAP content of various foods. Especially, the FODMAP content of foods consumed during exercise has received little attention (18). A limited number and variety of specialty sports foods (e.g. energy bars, gels) have been analyzed for FODMAP content. All of the products analyzed to date are classified as high FODMAP (Low FODMAP Diet App, Monash University, Melbourne, VIC, Australia) (20). Athletes desiring to consume low FODMAP products have little information on the FODMAP content of many popular sports nutrition products and examining ingredient labels might not be enough to accurately predict FODMAP content (16).

Given the challenges of the low-FODMAP diet, alternative approaches that decrease the FODMAP load being presented to the colon may prove more feasible.  

References:

1. Gibson PR, Shepherd SJ. Evidence-based dietary management of functional gastrointestinal symptoms: The FODMAP approach. J Gastroenterol Hepatol. 2010;25:252–258.
2. Staudacher HM, Irving PM, Lomer MC, Whelan K. Mechanisms and efficacy of dietary FODMAP restriction in IBS. Nat Rev Gastroenterol Hepatol. 2014 Apr;11(4):256-66.
3. Halmos EP, Power VA, Shepherd SJ, Gibson PR, Muir JG. A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology 2014; 146:67–75.e5.
4. Mitchell H, Porter J, Gibson PR, Barrett J, Garg M. Review article: implementation of a diet low in FODMAPs for patients with irritable bowel syndrome-directions for future research. Aliment Pharmacol Ther. 2019 Jan;49(2):124-139.
5. Staudacher HM, Whelan K. The low FODMAP diet: recent advances in understanding its mechanisms and efficacy in IBS. Gut. 2017 Aug;66(8):1517-1527.
6. de Oliveira EP, Burini RC, Jeukendrup A. Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations. Sport Med. (2014) 44(Suppl. 1):79–85.
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11. Lis, D., Ahuja, K.D.K., Stellingwerff, T., Kitic, C.M., and Fell, J. 2016. Case Study: Utilizing a Low FODMAP Diet to Combat Exercise-Induced Gastrointestinal Symptoms. Int. J. Sport Nutr. Exerc. Metab. 26(5): 481–487.
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17. Jeukendrup AE. Carbohydrate feeding during exercise. Eur J Sport Sci. (2008) 8:77–86.
18. Killian LA, Muir JG, Barrett JS, Burd NA, Lee SY. High Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols (FODMAP) Consumption Among Endurance Athletes and Relationship to Gastrointestinal Symptoms. Front Nutr. 2021 Apr 20;8:637160.
19. Lis DM, Kings D, Larson-Meyer DE. Dietary practices adopted by track-and-field athletes: gluten-free, low FODMAP, vegetarian, and fasting. Int J Sport Nutr Exerc Metab (2019) 29:236–45.
20. Lis DM. Exit Gluten-Free and Enter Low FODMAPs: A Novel Dietary Strategy to Reduce Gastrointestinal Symptoms in Athletes. Sports Med. 2019 Feb;49(Suppl 1):87-97.
21. Hill P, Muir JG, Gibson PR. Controversies and recent developments of the low-FODMAP diet. Gastroenterol Hepatol (N Y) 2017;13(1):36–45.