In this article accredited Sports Dietitian Cushla Holdaway (below) gives us the run down what nutrition no-no's we need to be aware of on race day to avoid gut irritation or worse.
Are you race day ready or playing rest room roulette? Let’s cover some frequently overlooked gastrointestinal (GI) irritants which can play havoc on your gut come race day…
1. LIMIT FIBRE
Nutritious and plant-based foods are essential for everyday wellness being rich in micronutrients and dietary fibre, but fibre is not something you want to overdo in your final days prior to, or morning of a race. Reducing total dietary fibre and higher FODMAP foods is recommended pre-exercise (1, 4).
2. Sugar alcohols and sweeteners. The ‘P’ in the acronym FODMAPs stands for polys and sugar alcohols. These generally aren’t tolerated well by most people, especially if consumed in larger quantities. Sneaky places these can hide is in sugar-free electrolytes, pre-workout supplements, chewing gums, and high protein/low carb products. Common examples include sorbitol, xylitol and mannitol (2).
3. CAFFEINE CAUTION Caffeine is one of the most researched performance enhancing supplements, but it has a sweet spot for dosing. Everyone has varying levels of tolerance, and it pays to be cautious pre-race, particularly if nerves and anxiety and already high (3).
4. DAIRY (context is key). Lactose intolerance is common, and if you know you are more sensitive to this then it would be wise to consider how much is consumed before a race. The highest lactose-containing dairy foods include cream, ice cream and cow’s milk.
5. HYPERTONIC PRODUCTS Hypertonic means a higher osmotic pressure than bodily and intracellular fluids. Most gels and some sports drinks (depending how concentrated they are made) fall into this category.
Hypertonic fluids require additional fluid to be drawn into the gastrointestinal track to assist digestion, which can increase the risk of GI distress. Practising with your race day nutrition in training is essential to working out your individual tolerance to various products and your fuel preferences.
6. PAINKILLERS (NSAIDS) Common non-steroidal anti-inflammatory medications (NSAIDs) such as ibuprofen and naproxen work wonders on inflammatory pain, but it comes with risks especially with GI function and kidneys. Caution is advised and these medications are generally strongly discouraged in endurance sports (1, 5).
7. RACE-DAY ANXIETY Excess nerves and anxiety can play havoc on the bowels due to the gut-brain connection (6). Working with a sports psychologist for management tools on race day as well as hypnotherapy can be useful. There is emerging evidence of hypnotherapy as a treatment in managing and improving symptoms of IBS (7).
8. NOTHING NEW ON RACE DAY This one’s a no brainer! That goes for nutrition, clothing, shoes, routine etc. It’s not worth the risk!
9. FIZZY DRINKS AND ALCOHOL Avoiding alcohol the night before an event goes without saying. Also be aware of fizzy or carbonated drinks, these can lead to gastrointestinal discomfort, particularly excess gas, bloating and belching.
References
1. 1 Costa RJS, Gaskell SK, Henningsen K, Jeacocke NA, Martinez IG, Mika A, Scheer V, Scrivin R, Snipe RMJ, Wallett AM, Young P. Sports Dietitians Australia and Ultra Sports Science Foundation Joint Position Statement: A Practitioner Guide to the Prevention and Management of Exercise-Associated Gastrointestinal Perturbations and Symptoms. Sports Med. 2025 May;55(5):1097-1134. doi: 10.1007/s40279-025-02186-6. Epub 2025 Apr 7. PMID: 40195264; PMCID: PMC12106582.
2. . 2 Barrett J, Collins L (2016, April 17. What are Polyols? https://www.monashfodmap.com/blog/what-are-polyols/
3. 3 The Australia Institute of Sport (AIS). (2021, March). AIS Sports Supplement Framework: Caffeine. file:///Users/cushlaholdaway/Downloads/1000498-quRDTmOloxKjnm0UhiR3XA%20(1).pdf
4. 4 Lower fodmap diet pre-exercise APA style: Montero-Carrasco, K., Arias-Tellez, M. J., & Soto-Sánchez, J. (2024). Use of Carbohydrate (CHO), Gluten-Free, and FODMAP-Free Diets to Prevent Gastrointestinal Symptoms in Endurance Athletes: A Systematic Review. Nutrients, 16(22), 3852. https://doi.org/10.3390/nu16223852
5. 5. Pham H, Spaniol F. The Efficacy of Non-Steroidal Anti-Inflammatory Drugs in Athletes for Injury Management, Training Response, and Athletic Performance: A Systematic Review. Sports (Basel). 2024 Nov 6;12(11):302. doi: 10.3390/sports12110302. PMID: 39590904; PMCID: PMC11598303.
6. Lydiard RB. Irritiable Bowel Syndrome, Anxiety, and Depression: What Are the Links? J Clin Psychiatry 2001;62[suppl 8]:38-45.
7. Hypnotherapy: Adler, E.C., Levine, E.H., Ibarra, A.N., Boparai, E.S., Hung, Y.-Y., McCrary, Q.D. and Lee, J.K. (2025), Gut-Directed Hypnotherapy for Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis. Neurogastroenterology & Motility, 37: e70037. https://doi.org/10.1111/nmo.70037
About Cushla
Cushla is an Accredited Sports Dietitian based in Mid-Canterbury, specialising in nutrition for endurance athletes from beginners to elites.
With a BSc in Human Nutrition and a Master of Dietetics (dist), she offers personalised consultations across New Zealand, both in-person and online. Cushla is also the dietitian for the New Zealand Defence Force (Burnham), runs online education courses, and hosts a podcast ‘Nourish Your Potential.’
Passionate about running and evidence-based nutrition, she helps athletes optimise performance and health through practical, realistic, and individualised advice.
Website: www.holdawaydietitian.com
Instagram: @cushlaholdaway_dietitian