Ultramarathon Nutrition: Training & Racing

The ISSN's recommendations for ultra-marathon training prioritize meeting individual caloric needs using a personalized and periodized nutritional strategy. This involves a varied diet, emphasizing whole foods. The plan should be implemented well in advance of the race to allow time for the body to adapt. The key is to create a strategy that is tailored to the individual runner's needs and training schedule, adjusting the plan as training intensity and volume changes throughout the season. A successful strategy will balance different macronutrients to allow the body to maximize its efficiency and achieve optimal results. This individualized approach recognizes the unique metabolic demands placed on each athlete.

The document strongly supports including a moderate-to-high carbohydrate diet (around 60% of total energy intake, or 5-8 grams per kilogram of body weight daily) to combat the negative effects of chronic glycogen depletion caused by intense training. This emphasis on carbohydrate intake highlights its importance in fueling endurance activities and maintaining energy levels, especially during prolonged exercise. Glycogen depletion is detrimental to performance and can lead to increased stress hormones and immune dysfunction. The recommended carbohydrate intake aims to prevent this depletion and support optimal athletic performance. Athletes need to understand how their bodies respond to carbohydrate intake to optimize energy levels and avoid exhaustion.

Optimal recovery and performance depend on meeting daily protein needs. The document highlights the importance of protein intake for muscle growth and/or maintenance in ultra-marathon runners. Adequate protein is vital for repairing muscle tissue damaged during intense training and competition, contributing to overall recovery and reducing susceptibility to injury. The recommended daily intake varies depending on the individual's training volume and caloric requirements, generally exceeding 1.6 grams per kilogram of body weight per day for those with high demands. Runners should consider their training intensity, caloric needs, and age when determining their individual needs.

The statement emphasizes the significance of adequate hydration during training and recovery. Inadequate hydration and/or rehydration can lead to performance reductions in subsequent training sessions and chronic health problems. It also discusses the potentially fatal consequences of poor electrolyte management, such as exercise-associated hyponatremia (EAH). The text stresses the importance of maintaining proper fluid balance throughout the training process. Individualized strategies for hydration are highlighted, emphasizing the need to understand personal sweat rates and adjust fluid intake accordingly. This section stresses that proper hydration is not just about drinking water, but also about maintaining proper electrolyte balance.

While many amateur ultra-marathon runners recognize the importance of nutrition, many neglect basic recommendations. The document notes that, although most amateur ultra-marathon runners understand that nutrition is key to success, many fail to apply the necessary information in their training regimen. While successful race completion is associated with greater energy and fluid intake, some athletes consume only 36–53% of their racing energy expenditure. The need to implement nutritional strategies aligned with the physical demands of training and racing is highlighted. This emphasizes the importance of bridging the gap between knowledge and practice to improve performance and recovery.

The primary aim of ultra-marathon training nutrition should be to maximize fat metabolism to conserve muscle glycogen stores. This approach prioritizes nutritional strategies that promote or optimize fat oxidation. The rationale behind this strategy is that by utilizing fat as a primary fuel source during training, the body preserves muscle glycogen, the primary energy source used during high-intensity phases of a race. This ensures that glycogen stores are available for when the athlete needs them most - the latter stages of the competition. This approach requires strategic macronutrient planning and careful timing of food consumption.

Carbohydrate pre-fuelling within 90 minutes of a training session, especially with high-glycemic foods, should be avoided. High-glycemic carbohydrate consumption leads to insulin secretion, which suppresses fat lipolysis. This is counterproductive to the goal of maximizing fat oxidation during ultra-marathon training. While pre-exercise carbohydrate intake facilitates glucose uptake into muscle and suppresses liver glycogenolysis, it can increase the risk of hypoglycemia in susceptible individuals. The overall recommendation here is to commence training in a euglycemic state, avoiding the insulin response to pre-exercise carbohydrates. Such pre-training strategies are meant to allow the body to adapt to using fat as fuel.

The 'train-low, compete-high' strategy is presented as a viable approach to enhance fat oxidation. This involves training with lower, but not depleted, glycogen stores to induce adaptations that increase total work capacity after glycogen resynthesis. This approach is supported by contemporary guidelines suggesting that endurance athletes should consume roughly 60% of their daily calories from carbohydrates, aiming for 5-12 grams per kilogram of body weight daily depending on training duration. This daily intake is important for restoring muscle and liver glycogen, meeting metabolic needs, and ensuring sufficient carbohydrate availability for subsequent days of training. However, chronically training with slightly reduced glycogen stores induces metabolic adaptations that enhance fat oxidation and ultimately increase total work capacity and time to exhaustion.

High-fat, ketogenic diets are discussed as another means of shifting metabolic flexibility towards fat oxidation. Traditional ketogenic diets involve a significant reduction in carbohydrate intake, usually with a 4:1 fat-to-protein or fat-to-carbohydrate ratio. Modified ketogenic diets (70% of energy as fat) might be more sustainable. While early studies suggested ergogenic effects, critiques cited limitations such as small participant numbers and lack of consideration for individual responses. More importantly, the findings from short-term studies may not apply to the typical training durations of ultra-marathons. The benefits of increasing fat metabolism are highlighted, but significant negative side effects, such as fatigue, nausea, and decreased micronutrient intake, are cautioned against. Overall, while ketogenic approaches may increase fat oxidation, sustained use for ultra-marathon performance remains inconclusive and should be approached with caution.

The substantial energy expenditure during ultra-marathons makes it impossible to fully meet caloric demands during the race itself. Calculations show a significant caloric expenditure, for example, a 50kg athlete completing a 50-mile race at 8km/h would expend roughly 3460kcal, while a 70kg athlete would expend approximately 4845kcal. For a 100-mile race at a slower pace, the energy expenditure increases dramatically, reaching around 6922kcal for a 50kg athlete and 9891kcal for a 70kg athlete. These high energy demands emphasize the importance of effective pre-race and post-race nutritional strategies to minimize caloric deficits and support recovery. The energy requirements are highly variable, depending on both the athlete's weight and the race distance.

The ISSN recommends a caloric intake of roughly 150–300 kcal/hour for races up to 50 miles (81km), acknowledging that some caloric deficits might be tolerated. For longer races where larger caloric deficits are less easily tolerated, the recommended intake increases to 200-400 kcal/hour. These recommendations are based on energy expenditure estimates and research findings. However, these are general guidelines, and individual tolerance, race pace, and gut comfort should be taken into account. If GI distress occurs, reducing caloric intake towards the lower end of the suggested range may be necessary. The recommendation emphasizes the need for a flexible approach and careful consideration of individual needs and race conditions.

Successful ultra-marathon completion is generally linked to higher energy and fluid intake, even when considering performance time variation. In longer races, the slower average work rate allows for faster gastric emptying, enabling higher energy intake and calorie-dense food consumption, up to the athlete's tolerance. Research indicates a wide range of carbohydrate intake among ultra-marathon runners, with some studies reporting intakes of 30 g/hour to as high as 65.8 ± 27.0 g/hour (range 36 -102 g/hour) in 100-mile races, significantly higher in finishers than non-finishers. Although high carbohydrate ingestion rates are advocated for shorter races, they might be unsustainable for ultra-marathons due to potential GI distress and the preference for fat and salt during these longer races. The slower pace in longer races makes this type of intake more manageable.

Protein intake during ultra-marathons is often overlooked, potentially due to its secondary role in energy metabolism and the logistical challenges of carrying and consuming sufficient amounts. However, protein ingestion may mitigate the negative effects of muscle damage and influence energy metabolism. Finishers of 100-mile races consumed significantly more protein than non-finishers (131.2 ± 79.0 g vs 43.0 ± 56.7 g), about twice as much when measured per hour (0.08 g·kg⁻¹·h⁻¹ versus 0.04 g·kg⁻¹·h⁻¹). There are conflicting results from controlled studies regarding protein supplementation. Despite this, the text still promotes higher protein intake to aid in muscle recovery and possibly mitigate central fatigue. Runners should carry and consume protein-rich foods and/or supplements throughout the race to support their needs.

Maintaining proper hydration is critical for thermoregulation during ultra-marathons, as the body relies on sweat evaporation for heat loss. Insufficient fluid replacement leads to dehydration, causing cardiovascular drift (reduced plasma volume and increased heart rate), diminished exercise capacity, increased risk of heat illness and rhabdomyolysis, and impaired cognitive performance. Dehydration negatively impacts performance and increases the risk of injury and illness, especially in challenging races. While dehydration can occur in cold conditions, it's more prevalent in hot and humid environments where sweat rates are higher. The text emphasizes that adequate hydration is essential for maintaining optimal physiological function during prolonged endurance activities.

Exercise-associated hyponatremia (EAH), a potentially fatal condition characterized by low serum sodium levels (<135 mmol/L), is a significant concern in ultra-marathons. EAH results from excessive sodium loss through sweat and/or the dilution of plasma sodium due to overhydration with low-electrolyte fluids. Early cases were observed in ultra-marathon runners and Ironman triathletes. While rare, individual susceptibility and prolonged sweating increase the risk, particularly in events exceeding marathon distance. The text warns against aggressive hydration strategies using low-electrolyte drinks, which can exacerbate the risk of EAH. The dangers of EAH and the critical need for proper sodium and fluid balance are explicitly discussed.

Runners should consume approximately 150–250 mL of fluid every 20 minutes during exercise, but intake should be adjusted based on environmental conditions, race duration, work rate, body mass, and individual fluid tolerance. Determining individual sweat rates beforehand, under conditions similar to race conditions, is crucial for optimizing fluid intake strategies. Measuring nude body mass before and after exercise provides a means to estimate sweat rate and guide fluid intake. Consuming 1000–2000 mg of sodium (NaCl) is recommended, but high sodium concentrations in fluids (>1000 mg/L) might negatively impact drink palatability. Capsules or tablets are preferable to liquid electrolytes to avoid compromising palatability. The need for a customized approach, factoring individual variables, is strongly emphasized.

Only a small percentage of endurance runners monitor their hydration status. While direct measurements like urine osmolality are not always practical, simple tools such as urine color charts and the Venn diagram (combining body mass, thirst, and urine color) can help estimate hydration. Pale-straw urine usually indicates good hydration. There is a need to emphasize the importance of adequate sodium intake, along with sufficient fluid, to prevent EAH. Runners should avoid low-volume drinking strategies, and should instead prioritize consuming adequate sodium, particularly in hotter conditions. Comprehensive education on the risks and consequences of EAH among ultra-marathon runners is essential to encourage better hydration and electrolyte management practices.

Gastrointestinal (GI) distress during ultra-marathon training and racing is a complex issue with multiple contributing factors. Reduced mesenteric blood flow, often caused by dehydration and/or increased core temperature, leads to GI hypoperfusion, impairing gastric emptying and paracellular transport. The disruption of intestinal tight junctions can allow systemic lipopolysaccharides (LPS) from gram-negative bacteria to enter the bloodstream, triggering an immune response and exacerbating GI distress. A study showed that a high percentage of runners requiring medical attention after a 56-mile ultra-marathon had elevated LPS levels and reported both upper and lower GI distress (nausea, vomiting, diarrhea). The prevalence of GI issues is highlighted, underscoring the need for strategies to mitigate this common problem in ultra-endurance events.

The high prevalence of GI symptoms in ultra-marathons is emphasized, with data indicating that the majority of athletes experience GI issues during races, particularly in the most challenging portions of the course. In a study of the Western States Endurance Run (100 miles), 96% of athletes experienced GI symptoms, with nausea being the most common and impactful issue. GI problems can significantly impact race performance, affecting the ability to consume adequate food and fluids. This highlights the importance of developing proactive strategies to prevent and manage GI distress in ultra-endurance events. These strategies should consider race conditions, environmental factors and individual tolerances.

The document suggests several strategies to limit the impact of GI distress. 'Training the gut' and personalized dietary approaches are presented as potential solutions. The text suggests that ultra-marathon training can lead to physiological adaptations and improved tolerance to certain foods, enhancing intestinal tight-junction integrity and the immune response to endotoxin release. Well-trained athletes may tolerate higher carbohydrate intakes, and habituation to a high-carbohydrate diet can improve carbohydrate oxidation rates. Low FODMAP diets are suggested to help athletes with irritable bowel syndrome (IBS). These modifications can be incorporated into an individual training and racing program to minimize GI upset.

Using solutions containing multiple transportable carbohydrates (glucose, fructose, maltodextrin) increases intestinal absorption, improves carbohydrate oxidation rates, and reduces GI discomfort compared to single carbohydrate solutions. While ultra-marathon runners often don't solely rely on sports drinks, such solutions offer a short-term strategy for managing energy intake and preventing non-completion. Maintaining energy intake close to target values, even in the face of nausea, is suggested. Probiotic bacteria (Lactobacillus and Bifidobacterium species) can modify gut microbiota and support GI health. Studies indicate reduced GI symptoms with probiotic supplementation, though benefits vary by strain. While pre/probiotics show potential, limited evidence exists for ultra-marathon racing, so caution is urged.

Caffeine, widely consumed, shows ergogenic effects in various sports, although the extent varies due to individual genetic differences. It acts centrally by blocking adenosine receptors, improving cognitive function and concentration, and peripherally by potentiating intramuscular calcium release, enhancing muscle contractile function. However, side effects like GI distress, headaches, and anxiety are possible. Caffeine use should be carefully planned and practiced before competition; while reducing habitual intake before competition might enhance race-day sensitivity, this is debated. The text emphasizes that athletes should have a plan in place for caffeine use, carefully considering both the benefits and potential downsides.

While enhanced fat oxidation might be promoted by nutritional ketosis, current evidence doesn't support an ergogenic effect from MCTs or ketone esters compared to moderate-to-high carbohydrate diets. MCTs, proposed to enhance aerobic metabolism, show limited impact on fuel utilization in human studies, even in low-glycogen states. To minimize GI distress, MCT oil should be consumed in small amounts (<30g), further reducing potential benefits. The text concludes that although there are theoretical reasons to consider MCTs and ketone esters, the actual data does not yet support their use for ultra-marathon performance.

There's limited evidence supporting vitamin and mineral supplementation for ultra-marathon performance, except in cases of clinically diagnosed deficiencies. A study showed no significant performance differences between supplemented and non-supplemented athletes in a 4-week trial. Therefore, maintaining adequate nutrient intake through a balanced diet is emphasized, rather than relying on supplements. Antioxidant supplementation is discouraged due to its potential to blunt exercise-induced physiological adaptations. The text emphasizes that appropriate micronutrient intake is generally best achieved through diet, not supplements, unless a specific deficiency has been diagnosed.

L-glutamine, an abundant amino acid vital for immune function, might support GI epithelial integrity, particularly in combination with probiotic use. A study showed that L-glutamine supplementation reduced GI permeability after demanding exercise in a controlled setting, suggesting a potential dose-response relationship. However, the evidence is not strong enough to recommend L-glutamine for athletes seeking to mitigate immunodepression. Further research in the context of ultra-marathon running is needed to confirm its efficacy and optimal dosage. The text cautions that, while there is potential for benefit, more research is needed before a recommendation can be made.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are strongly discouraged due to increased risk of GI injury, exacerbated in long-distance runners prone to GI bleeding. Prophylactic NSAID use also increases the risk of renal side effects and may contribute to exercise-associated hyponatremia. The lack of conclusive evidence for their efficacy and the potential for serious adverse effects make NSAIDs unsuitable. Non-NSAID analgesics (like paracetamol) are not performance-enhancing but performance-enabling, with better tolerability but caution urged against masking pain that might indicate injury. The text emphasizes the importance of paying attention to pain signals as indicators of potential problems.