Written by Kim Young, RD.
Kim has been a dietitian for over 15 years. She’s been competing in triathlons and running events for over 20 years and has been a consultant with a variety of sports clubs.
You can email Kim at kimyoung.rd@gmail.com or visit http://www.dietitians.ca/Your-Health/Find-A-Dietitian/Find-a-Dietitian.aspx to find a dietitian specializing in sport nutrition to help you develop an individualized training and racing nutrition plan.
Training and preparing for a marathon takes a training plan and dedication. How you are going to nourish your body to prepare for and complete the event can support your preparation and ensure that you execute you optimal performance. This article discusses the important points to consider when planning your marathon nutrition racing strategy.
Carbohydrates
Although many people recognize that carbohydrates are important for exercise, it is not uncommon for marathon runners to underestimate what is required for optimal race performance. Carbohydrates are the major source of fuel during a marathon race. The sources of carbohydrates that the body uses are muscle glycogen (one of the stored form of carbohydrates in your body) and what you intake during the race. Other sources of energy that the body uses during the race are fatty acids, liver glycogen and small amounts of amino acids.
The higher the intensity at which you exercise, the greater the reliance your body is going to have on your muscle glycogen and the carbohydrates you provided it during exercise. It has been suggested that over 90% of your energy requirements during a marathon race will come from these two sources.
Carbohydrate Loading
Muscle glycogen stores are a limiting factor when it comes to marathon performance. Increasing the carbohydrates in your diet before the marathon can promote carbohydrate loading of your muscle glycogen stores. This practice should be done in conjunction with a training taper and appears to benefit men more than women. Approximately ever gram of carbohydrate stored in the muscle will be stored with an additional 3 millilitres of water. As a result you can expect to gain a couple of pounds before the race. For this reason some athletes choose to forgo using this pre-race nutrition strategy.
Over the last few decades several carbohydrate loading protocols have been developed. The simplest one is to increase your carbohydrate intake by between 8 - 11 grams of carbohydrate per kilogram of body weight per day over 1 - 2 days before the race. This can be a substantial intake of carbohydrates and translates to about 700 g of carbohydrates for a 155 pound (70 kg) person. That is the equivalent of about 2 loaves of bread! (Do not consume all the carbohydrates as bread.)
Many carbohydrate rich foods can be a source of fibre. Increasing your fibre intake the days leading into a marathon is NOT recommended. Therefore if you choose to try using a carbohydrate loading strategy, you are best to look at using low fibre carbohydrate sources such as sugary beverages, juices, and white grain products. (On a personal note, I like to buy a bag of hard candies and suck on them over the course of the day or two prior to an endurance event. I’ve also been known to drink regular pop and order fries rather than having my usual side salad and water with meals during this time.)
Pre-Race Meal
How much carbohydrate your pre-race meal contains depends on the amount of time between when your race starts and when you plan to eat your pre-race meal. As a general rule, for every hour before your race, consume 1 gram of carbohydrate per kg of body weight. Therefore if you are a 155 pound (70 kg) athlete and are planning on eating breakfast 2 hours before your marathon start time, you would try to consume about 140 grams of carbohydrates prior to the race. It is also important that your pre-race meal leaves you feeling comfortable (i.e. not full and bloated, not hungry) on the start line.
An example of what about 140 g of carbohydrates may look like include:
· 1 bagel (60 g carbohydrate)
· 1 large banana (25-30 g carbohydrate)
· 1 tablespoon of honey (10-15 g carbohydrate)
· 12 ounces (330 ml) juice (40-45 g carbohydrate)
Race Carbohydrate Intake
Higher intakes of carbohydrate per hour are associated with improved results in endurance events. Historically, carbohydrate recommendations have been between 30 to 60 grams per hour while performing endurance exercise. More recently, it has been suggested that this limit can be increased up to 90 grams per hour by using mixed sources of carbohydrates, such as a combination of both glucose and fructose.
Race Carbohydrate Intake
Higher amounts of carbohydrates can put you at risk of having gastrointestinal issues if you are not use to taking in this much. If this is a problem, you may be able to train your gut to tolerate higher carbohydrate levels. If you are considering trying to push the higher limits, work on doing this during training and slowly overtime.
It is best to develop your own nutrition strategy using carbohydrate sources that are acceptable to you both from a taste, mouth feel and gastrointestinal tolerance perspective. Often carbohydrate sources are in the forms of sports drinks, gels or gummies/ candies. Some people choose more whole foods such as dried fruits, diluted fruit juice, honey or syrup. Whatever your choice is, it is important that you have tried these foods and drinks during training, and ideally in a training race, as intensity can play a role in your personal tolerance.
Fluids
In the days leading into the marathon, ensuring that you keep hydrated is important. If you choose to increase your carbohydrate intake in efforts to carbohydrate load, you will require additional fluid. The best way to monitor your hydration status is through the frequency and color of your urine. A pale straw coloured urine is a sign that you’re well hydrated, but if you take high doses of vitamins, your urine colour may not be a good indicator.
During the race, consume enough fluid to avoid losing more than 2% of your body weight, but do not try to equal your sweat losses. A fluid intake of between 400 to 800 ml per hour accommodates most athletes’ needs. Special considerations include the size and fitness of the athlete, as well as the environmental conditions. Overdrinking (or over-hydration) during endurance exercise is the main cause of hyponatremia (low blood sodium levels). People who are at the greatest risk for this are those who are smaller, or run a marathon in over 4 hours, therefore often women.
Sodium
Sodium intake during marathon events is recommended. The amount needed is highly variable and there is no general consensus. On average, sweat contains about 1 gram of sodium per litre, but this is also variable among individuals. Consuming 400 to 800 mg of sodium per hour of exercise is a reasonable range to aim for. If you are choosing to use sodium tablets during your race, be sure to try them out in a training race or intense long workout. Individuals that need higher sodium intakes include heavy sweaters or those who may not be acclimatized to hot racing environments.
Caffeine
The effect of caffeine is individualized. How a cup of coffee affects you prior to a race may be quite different than the effect it has on your training partner. If you are planning on including caffeine in your race routine make sure that you have tried it out in practice, and remember that caffeine may enhance any nervous jitters you may experience. Possible benefits of caffeine include increased fat oxidation and less reliance on glycogen stores during moderate to intense physical activity. In addition, caffeine can have other benefits such as improved alertness, mood and cognitive function. These are all important parts of a marathon, especially in the later stages. Research suggests that caffeine intake of about 2 to 3 mg per kilogram of body weight (or approximately 200 mg) before and/or during exercise can enhance performance.
Many sport nutrition products now include caffeine in varying amounts. If you are considering adding caffeine into you marathon routine, read the labels and do a bit of math to find the right amount for your plan. An example of how you may include it at the recommended doses includes a 8 to 12 ounce coffee about an hour before your race, and using caffeine containing gels during your race to provide between a total of 100 to 200 mg of caffeine over the course of your race.
Hot racing environments
Racing in hot environments puts additional stress on the body. It is suggested that the optimal marathon temperature is 5 to 10 oC and finishing times begin to increase by about 0.03% for every 1oC above this ideal range, with decreases in performances topping out between 12-17% at temperatures in the high 20oC range.
Nutrition related heat stressors include the body’s decreased ability to use fatty acids or the carbohydrate consumed during exercise. In addition, there’s an increased reliance on muscle glycogen. Keeping your body temperature down prior to and during the race will help relieve some of this metabolic stress. Nutrition strategies include sipping on cold drinks, or chewing on ice chips or freezies prior to the race. On the race course, look for opportunities to drink cold liquids, or consume ice or slushies. (Of note, freezie pops were unexpectedly handed out during the 2016 Boston marathon…a nice surprise for those struggling with slightly warmer conditions.)
Planning
Planning your nutrition
What you plan to eat before and consume during your race should be planned out weeks to months in advance of race day. Ideally, practice your pre-race nutrition before long runs or before less significant racing events. During exercise and less significant races, practice consuming the forms of carbohydrates you plan to consume during your marathon. Do your homework and determine how frequently aid stations will be placed on the marathon race course and what will be provided.
Know that you may not get it right the first time and learn from experience. If a strategy does not work, evaluate it and reflect on what you will do differently next time. The more work you put into your nutrition plan the more confident you will be on race day. This will decrease your likelihood of breaking the rule of not trying something new on race day, and increase the likelihood you will executing your optimal race performance.
References:
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Nutrition and athletic performance. Position of dietitians of Canada, the academy of nutrition and dietetics and the American college of sport medicine. Feb 2016. Available at www.dietitians.ca/sports
Spriet L. Exercise and sport performance with low dose of caffeine. Sports Med. 2014;44(Supp 4):S175-84.
Jentjens R, Wagenmakers A, Jeukendrup E. Heat stress increases muscle glycogen use but reduces the oxidation of ingested carbohydrates during exercise. J Appl Phys. 2002;92(4):1562-72.
Jones P, Barton C, Morrissey D, et al. Pre-cooling for endurance exercise performance in the heat: a systematic review. BMC Medicine. 2012;10:166
Tan S, Lee J, The role of fluid temperature and form on endurance performance in the heat. Scand J Med Sci Sports. 2015;25(sup 1):39-51
El Helou N, Tafflet M, Berthelot G, Tolaini J, Marc A, et al. Impact of environmental parameters on marathon running performance. PLoS ONE. 2012;7(5);e37407. doi:10.1371/journal.pone.0037407. Available online.
