Athletes, particularly in endurance sport, implement various dietary practices such as a low residue diet or lactose elimination to reduce the risk of exercise-associated gastrointestinal (GI) distress. GI symptoms are multifactorial, transient, challenging to replicate and influenced by placebo effect, so the true efficiency of dietary strategies require tailoring to the individual. This is further complicated by the fact that an implemented plan may be successful one race and not for the next. Recently, a more novel dietary approach was tested in runners with persistent exercise-associated GI distress: a short-term low FODMAP diet (2). In this previous articles we explained what FODMAPs are.
Many athletes avoid foods high in FODMAPs, such as lactose or legumes, with the aim to reduce GI symptoms and there seems to be a high rate of perceived symptom improvement (4). Repeated stress placed on the gut combined with high carbohydrate intakes and high FODMAP loads present in many sports foods may create the perfect storm for FODMAPs exacerbating exercise-associated GI symptoms. Exercise stress is known to impair gut motility and permeability and epithelial injury and it is plausible that preexisting FODMAPs in the GI tract, such as the high fructan pasta meal eaten the night before a race, or ingested during strenuous exercise (e.g. dried dates and oats in energy bars) could increase osmotic load and colonic gas volume, whereby worsening symptoms. Connecting this clinical concept, a short-term (6-day) low FODMAP diet was tested in healthy runners with persistent moderate to severe exercise-associated GI symptoms to see if symptoms during running and daily (symptoms occurring outside of exercise but potentially influenced by exercise stress) could be reduced.
In a recent cross over study (1), recreationally competitive runners with self-reported GI symptoms were given both high (~41 g FODMAPs/day) or low FODMAP (~8 g FODMAPs /day) diets. The diets were similar with minor modifications of ingredients to achieve varying amounts of FODMAP content. Runners were told they were being given ‘specific carbohydrate diets’ with pre-made and frozen meals and snacks supplied. Interestingly, usual FODMAP intake was checked before the study and all participants ate a high FODMAP diet (~43 g FODMAPs/day), similar to the high FODMAP diet given in the study. During each intervention period the runners completed two hard runs: one 5 x 1000m interval, and a 7km threshold run (2).
On the low FODMAP diet 9 of 11 runners reported fewer and/or less severe GI symptoms daily throughout the study on the low-FODMAP diet. Incremental area under the curve (AUC), which is an overall measure of how much GI distress an individual experienced during each diet, also confirmed that symptoms were lower with the low FODMAP diet. Although, during exercise GI symptoms were not clearly different this might be distinguishable in future research that integrates harder and longer bouts of exercise.
Overall, this preliminary work suggests a low FODMAP approach may be promising tool to add to the practitioners’ toolbox for the treatment of exercise-associated GI syndrome. It is important to note that clinically healthy endurance athletes with exercise-associated GI syndrome do not instinctively require a low FODMAP diet. However, it may be a tool to reduce symptoms in certain individuals. If the plan is to follow low FODMAPs for a long time then it is advisable to determine the exact FODMAPs that are triggers (through FODMAP elimination and reintroduction), as it is unlikely that every food high in FODMAPs will amplify GI symptoms for all individuals. Athletes are encouraged to avoid unnecessary dietary restriction as a full low FODMAP diet can be quite restrictive. Moving forward, if a low FODMAP approach is being considered, work with an experienced practitioner to become properly educated and steer clear of the nonsense likely to be associated with the predicted food industry boom in the low FODMAP trend.
Costa RJS, Snipe RMJ, Kitic CM, Gibson PR. Systematic review: exercise-induced gastrointestinal syndrome-implications for health and intestinal disease. Aliment Pharmacol Ther. 2017;46(3):246-265.
Lis DM, Stellingwerff T, Kitic CM, Fell JW, Ahuja KDK. Low FODMAP: A Preliminary Strategy to Reduce Gastrointestinal Distress in Athletes. Med Sci Sports Exerc. 2017;10.1249/MSS.0000000000001419. In press.
Staudacher, Irving PM, Lomer MC, Whelan K. Mechanisms and efficacy of dietary FODMAP restriction in IBS. Nat Rev Gastroenterol Hepatol. 2014;11(4):256-66.
Lis D, Ahuja KD, Stellingwerff T, Kitic CM, Fell J. Food avoidance in athletes: FODMAP foods on the list. Appl Physiol Nutr Metab. 2016;41(9):1002-4.