^{Kate Burrage, RD is a registered dietitian at Vancouver General Hospital and seasoned marathon runner. She has given numerous presentations about proper nutrition for runners, specifically marathon runners. This article is the handout accompanying her presentation. Copyright © by Kate Burrage. Unauthorized reproduction of this article is prohibited. The complete article s available in PDF format.}

Nutrition for Optimum Marathon Performance

Overview

Overall, the best thing you can do for marathon performance is to eat a balanced diet, including a variety of foods from all four food groups. Refer to Canada's Food Guide for more detail about the food groups and how many servings from each group you need in a day.

Fuel for your muscles comes from fat and carbohydrate (glucose).

Fat stores are unlimited but carbohydrates are not stored well by the body so there is the potential to run out of glucose as an energy source during endurance events.

• The liver and muscles store a limited amount of glucose as glycogen.
• Because glucose isn't stored well, you will need to consume carbohydrates during long runs. This glucose will be absorbed into the blood to help fuel your muscle cells.

Use your long Sunday runs to experiment with what works best for you and when you find that magic combination, don't change anything for race day. That way there are no surprises.

Before a Run or Race

Try to start your run with full glycogen stores and some carbohydrate in the stomach to help maintain blood glucose levels to provide fuel for your muscles. Eat a meal 2-4 hours before the run, including about 1gram/kg of carbohydrates and about 2 cups (500 ml) of fluid.

In the hour immediately prior to the exercise (or half hour if you can tolerate it), have some easily digested carbohydrates; for example a sports gel, a sports drink, jelly beans, Sharkies. In addition, try to have another 1 cup of fluid (if you have a sports drink, the fluid is included).

During a Run Lasting more than an Hour or on Race Day

Take 30-60 g of carbohydrates every hour. 1 gel supplies about 25g, sports drinks supply about 14g per cup, 13 Sharkies supply 42g. Read the label of your favourite product. Sports nutrition products will also provide electrolytes, which are important, especially in hot weather.

Estimated fluid losses during running in moderate weather (ie: Vancouver) are 1000-1500mL per hour. It is very difficult to drink this much while running, but research has shown that for every liter of water lost the heart rate is elevated by 8bpm, cardiac output is decreased by 1l/min, and body temperature rises by 0.3°C.

Make drinking on the run a habit, even during shorter runs. Drinking small amounts often is usually better tolerated. Aim for 1-2 cups every 15 minutes. The closer you can match your fluid losses, the better your performance will be.

Try weighing yourself before and after a run to see how much water you are losing. During a marathon, you should only lose a few pounds if you are hydrating adequately.

Recovery

There is a 30 minute window after a run when your muscles are primed to take up glucose and replenish glycogen stores for your next run. If you can eat 50-100 g of carbohydrates in this window, along with 10-20 g of protein, this will aid in muscle recovery more than eating later.

For every pound of weight that you lose during exercise, drink 2.5 cups of fluids.