Race Day Nutrition to Maximize Performance And Minimize Gastrointestinal Distress

What you eat the morning of your ultra and even more importantly what you eat during your race can make or break your race. The first thing to remember is carbs are king if you want to run faster. If you plan on power hiking the entire race, what you eat is less important, but if you are planning on running most (or all) of your next race focusing on food is huge. Races at altitude cause your body to work harder and carbohydrate (CHO) intake is even more important. 
​
​While running our bodies are using both CHO and fats for energy. Even the leanest runner has sufficient fat supplies to last for days but only enough CHO to last a couple hours. That is why CHO intake in the days leading up to a race, race morning, and during the race are important. 

Coach Matt running the Gorge 50k in Oregon by Daybreak Racing and Freetrail. Photo by James Holk

​Daily needs for CHO for an ultra-runner are 6-12g/kg body weight. The lower end for athletes running an average of an hour a day and the higher end for athletes averaging 4+ hours of running a day. Protein (PRO) while not used as a primary energy source is essential to maintain muscle mass and cellular function and repair. Daily needs for PRO for ultra-runners are 1.2-2.0g/kg body weight per day. Again, the lower end is for athletes exercising less and the high end is for athletes exercising more and creating more weekly muscle damage. Most ultra-runners would be safe to consume 1.6-1.8g PRO/kg body weight. 

​Your pre-race meal is ideally 3 hours before the start of your race so that you can digest most of it and have those calories ready to fuel your race. Consuming some protein and fat is a good idea, but the main goal is lots of carbohydrates. Lower fiber and avoiding a lot of vegetables is a good idea to keep you running and out of the port-a-potties. 1-4g CHO/kg body weight is recommended in your prerace meal to ensure liver glycogen is maximized. 

​It is a good idea to avoid eating a gel or any high-glycemic food in the hour before a race because research has shown that can lead to the release of insulin which can lead to hypoglycemia early in the race. If you want to eat something in the hour before your race, it’s best to eat a low-glycemic CHO, like fructose and avoid high-glycemic CHO like glucose. As soon as you’re running you can start consuming high-glycemic foods and not have those negative side effects. 

​While running, it’s a lot easier on your stomach to digest small amounts of food continuously rather than large amounts infrequently. This means focusing on getting in calories constantly in small amounts. You can eat your calories, drink your calories, or do a combination of both to meet your calorie needs. Getting some food in at least every 20 minutes is ideal. Definitely avoid letting an hour or more go by without eating because then it’s a lot more likely your digestive system will shut down and cause you gastrointestinal (GI) distress and you’ll be much more likely to bonk. Those scenarios are best to avoid. 

There’s a term called Multiple Transportable Carbohydrates (MTC) that describes how glucose and fructose (two types of sugars) are absorbed in the body differently and when we consume both types, we can absorb more calories of CHO per hour than if we only ingest one type of CHO. Glucose is absorbed in the intestine by the sodium-dependent glucose transporter SGLT1, and fructose is absorbed in the intestine by the intestinal transporter GLUT 5 (or recently renamed SLC2A5). Research has shown people on average can absorb 60g glycose and 30g fructose per hour (360 calories from CHO), so it has been standard practice to recommend ingesting food to meet those numbers. Recent research however has shown that another glucose transporter GLUT2 (or SLC2A2) shows up almost instantly in the gut in response to the presence of glucose and allows athletes to absorb more than previously thought. Research has also shown that the gut is highly trainable in as little as two weeks. I’d recommend experimenting with increasing CHO intakes during training in the weeks prior to your race to figure out what amount your body can tolerate. 

​To train your gut and maximize CHO intake and performance, start with around 50g of carbs per hour (around 33g glucose and 17g fructose) during long runs and increase by 5-10g/hour each long run until you find your limit. Stick with that amount for several long runs but then try to increase your CHO intake again slightly (maybe by 5g/hour) as your gut adapts to higher CHO loads. Again, on average most athletes can absorb about 30g fructose/hour (120 calories from fructose) and between 60g and 90g glucose/hour. Some athletes have found they can consume 110g glucose/hour along with 30g/fructose/hour for a total of 140g/hour. 

Matt fueling with GU energy while running the Teton Crest Trail 40 mile run adventure with friends. Matt has trained his gut to handle 90-110g CHO/hour without issues. Photo by Andy Cochrane.

​Some sports nutrition products will list glucose or fructose on the label, but many will instead list other names for sugar. To understand what these ingredients mean, here’s a breakdown of the most common carbohydrates in sports nutrition products: 

​Dextrose: another name for glucose
Sucrose: 50% glucose 50% fructose
Maltodextrin: a chain of glucose molecules 
Cane Sugar/table sugar: same as sucrose – 50% glucose 50% fructose
Maltose: two molecules of glucose hooked together
Honey: about 50% glucose and 50% fructose
High Fructose Corn Syrup: about 50% glucose and 50% fructose 
Brown Rice Syrup: 52% malotriose, 45% maltose, 3% glucose. But maltotriose is three glucose molecules and maltose is two glucose molecules, so it is 100% glucose. 

​​Real foods like rice and wheat are mainly starches which break down into glucose. A potato is about 55% glucose and 45% fructose. A banana is about 50% glucose and 50% fructose, as are most fruits. Oreo cookies, gummy bears, Sour Patch Kids, and most candies are made with sugar, dextrose, corn syrup, and/or high fructose corn syrup and will have between a 50/50 to 60/40 glucose/fructose ratio. 

​As you can see, most foods trail runners consume while running will give you a mix of glucose and fructose. The shorter the race is (2-5 hours) the easier most athletes find it to eat just CHO, but as races get longer (6-24+ hours) most athletes find their palate demands things other than sugar, and often a little more protein and fat. At higher intensities it is difficult to digest fat and protein. As intensity decreases, which will naturally happen in longer races (6-24+ hours), it becomes easier for your gut to digest fat and protein. 

​One very promising ingredient in sports nutrition is Highly-Branched Cyclic Dextrin (HBCD) or Cyclic Cluster Dextrin (CCD). HBCD is made by fermenting corn starch to make a molecule of linked glucose units similar to glycogen. HBCD has been shown to decrease gastrointestinal upset, decrease gastric emptying time, decrease rating of perceived exertion, and improve endurance performance compared to typical glucose/fructose mixtures. Many athletes are finding that consuming a portion of their hourly glucose in the form of HBCD decreases GI distress and allows them to consume more CHO/hour. 

​Whether you eat or drink your CHO depends on many factors including ease of consumption, availability, personal preference, gut tolerance, sweat rate, and weather conditions. It is important to have a good estimate of individual sweat rates for different conditions and to make sure you match your water and electrolyte consumption accordingly. In cold and dry weather, you are going to need less water and in hot and humid conditions, more water. I’ll discuss hydration in detail in a future article. 

In summary, to help set yourself up for a great race, make sure you are consuming adequate carbohydrates in your daily diet, pre-race meal, and during your race. Most athletes find they do well by consuming 75+ grams (300+ calories) of CHO per hour, from a mix of glucose and fructose and possibly in the form of Highly-Branched Cyclic Dextrin. As with everything, experiment and practice your nutrition plan well in advance of your race to find what works for you. 

Matt Whitehead coaches ultramarathon runners at Ultra Run Coaching and helps athletes and non-athletes become pain free at Oregon Exercise Therapy. When not coaching athletes or doing posture alignment therapy, Matt can be found trail running and mountain biking around the Pacific NW with friends and his dog Lucky.

References: 
Costa RJS, Miall A, Khoo A, Rauch C, Snipe R, Canoes-Costa V, Gibson P. Gut-training: the impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance. Appl Physiol Nutr Metab. 2017 May;42(5):547-57.
 
de Oliveira EP, Burini RC. Carbohydrate-dependent, exercise-induced gastrointestinal distress. Nutrients. 2014 Oct13;6(10):4191-9.
 
de Oliveira EP, Burini RC, Jeukendrup A. Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations. Sports Med. 2014 May;44 Suppl 1(Suppl 1):S79-85.
 
Drozdowski L, Thomson ABR. Intestinal sugar transport. World J Gastroenterol. 2006 Mar21;12(11):1657-70.
 
Furuyashiki T, Tanimoto H, Yokoyama Y, Kitaura Y, Kuriki T, Shimomura Y. Effects of ingesting highly branched cyclic dextrin during endurance exercise on rating of perceived exertion and blood components associated with energy metabolism. Biosci Biotechnol Biochem. 2014;78(12):2117-9. doi: 10.1080/09168451.2014.943654. Epub 2014 Jul 31. PMID: 25080121.
 
Hargreaves M, Hawley JA, Jeukendrup A. Pre-exercise carbohydrate and fat ingestion: effects on metabolism and performance. J Sports Sci. 2004 Jan;22(1):31-8. doi: 10.1080/0264041031000140536. PMID: 14971431.
 
Jeukendrup AE, Killer SC. The myths surrounding pre-exercise carbohydrate feeding. Ann Nutr Metab. 2010;57 Suppl 2:18-25.
 
Jeukendrup AE, Moseley L. Multiple transportable carbohydrates enhance gastric emptying and fluid delivery. Scand J Med Sci Sports. 2010 Feb;20(1):112-21.
 
Kinrade EJ, Galloway SDR. Dietary Observations of Ultra-Endurance Runners in Preparation for and During a Continuous 24-h Event. Front Physiol. 2021 Nov 24;12:765888. doi: 10.3389/fphys.2021.765888. PMID: 34899391; PMCID: PMC8652078.
 
Koepsell H. Glucose transporters in the small intestine in health and disease. Pflugers Arch. 2020 Sep;472(9):1207-48.
 
Miall A, Khoo A, Rauch C, Snipe RJ, Canoes-Costa VL, Gibson PR, Costa RJS. Two weeks of repetitive gut-challenge reduce exercise-associated gastrointestinal symptoms and malabsorption. Scand J Med Sci Sports. 2018 Feb;28(2):630-40.
​
Shiraki T, Kometani T, Yoshitani K, Takata H, Nomura T. Evaluation of Exercise Performance with the Intake of Highly Branched Cyclic Dextrin in Athletes. Food Sci Technol Res. 2015;21(3):499-502.

Takii H, Hiroshi & Kometani, Takashi & NISHIMURA, Takahisa & Kuriki, Takashi & FUSHIKI, Tohru. (2004). A Sports Drink Based on Highly Branched Cyclic Dextrin Generates Few Gastrointestinal Disorders in Untrained Men during Bicycle Exercise. Food Science and Technology Research - FOOD SCI TECHNOL RES. 10. 428-431. 10.3136/fstr.10.428.

Takii H, Kometani T, Nishimura T, Kuriki T, Fushiki T. A sports drink based on highly branched cyclic dextrin generates few gastrointestinal disorders in untrained men during bicycle exercise. Food Sci Technol Res. 2004;10(4):428-431. doi:10.3136/fstr.10.428 

Takii H, Takii Nagao Y, Kometani T, Nishimura T, Nakae T, Kuriki T, Fushiki T. Fluids containing a highly branched cyclic dextrin influence the gastric emptying rate. Int J Sports Med. 2005 May;26(4):314-9. doi: 10.1055/s-2004-820999. PMID: 15900642.
 
Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016 Mar;48(3):543-68. doi: 10.1249/MSS.0000000000000852. Erratum in: Med Sci Sports Exerc. 2017 Jan;49(1):222. PMID: 26891166.
 
Urdampilleta A, Arriblazaga S, Viribay A, Castaneda-Babarro A, Seco-Calvo J, Mielgo-Ayuso J. Effects of 120 vs. 60 and 90 g/h carbohydrate intake during a trail marathon on neuromuscular function and high intensity run capacity recovery. Nutrients. 2020 Jul15;12():2094.
 
Viribay A, Arribalzaga S, Mielgo-Ayuso J, Castaneda-Babarro A, Seco-Calvo J, Urdampilleta A. Effects of 120 g/h of carbohydrates intakes during a mountain marathon on exercise-induced muscle damage in elite runners. Nutrients. 2020 May11;12(5):1367.
 
Wilburn, Dylan & Machek, Steven & Ismaeel, Ahmed. (2021). Highly Branched Cyclic Dextrin and its Ergogenic Effects in Athletes: A Brief Review. Journal of Exercise and Nutrition. 4. 10.53520/jen2021.103100.