Fueling your run with good nutrition

To train for and run a long-distance race requires a lot of energy. Good nutrition will give your body the fuel it needs to cross the finish line. The best advice I received while training for my first marathon was simple, yet effective: Eat when you're hungry. In other words, let your body be your guide. While eating enough is vital, what you eat is equally important.

Your body's muscles run on two primary fuel sources: carbohydrates and fat. Dietary carbohydrates are broken down into simple sugars called glucose. During the start of a run, your body pulls glucose from your bloodstream. When this is exhausted, the body then taps into stored glucose, called glycogen, in your liver and muscles. The rate at which glycogen is depleted depends on the intensity and duration of exercise and how much glycogen is stored..

When the glycogen is depleted, fat is then burned as a backup energy source. For fat to be used for energy, it must be broken down into fatty acids and other components, which requires time and makes it a less-efficient fuel source. Regular running also will train your body to be better at converting fat to fuel.

Long-distance runners should aim to get most of their calories from carbohydrates — the body's preferred fuel source. Choose complex carbohydrates, such as pasta, oatmeal and potatoes, for sustained energy. Before a long run, focus on simple carbohydrates that can be used immediately. Sources for these include fruit, regular sports drinks and energy gels.

During a long run or race — generally more than 90 minutes — aim to consume 30 to 60 grams of carbohydrates every hour. This goal can be met with beverages or food. Two cups of a regular sports drink contain about 30 grams of carbohydrates.

Because fats aren't quickly converted to energy, avoiding a high-fat meal before a run is best. Instead, make fats part of your meals throughout the day. Focus on healthy fats from seeds, nuts, fatty fish, hummus and avocados.

While protein isn't necessarily a fuel source during a run, it's essential for muscle repair after a run. Eating adequate protein will allow you to recover more quickly. Choose good sources of protein throughout the day at meals and within 30 minutes after a workout for optimal recovery. Good protein sources include meat, chicken, fish, eggs, dairy products, tofu and beans.

Specific needs for calories, carbohydrates, protein and fat differ from person to person and depend on age, gender, activity level and medical conditions. The months spent training for your race allow you time to optimize your diet. Most runners can figure out what works best for them with trial and error. However, seeking guidance from a registered dietitian can help simplify the process of fueling your run.

Try this orange juice smoothie for a pre- or post-run recovery snack. Orange juice is an excellent source of potassium, a mineral that helps regulate blood pressure and cell function. You lose potassium through sweating, and low potassium levels can reduce your energy and endurance.

Orange juice smoothie

Makes 2 servings

1 cup fat-free, no-sugar-added vanilla frozen yogurt
3/4 cup fat-free milk
1/4 cup frozen, no-sugar-added orange juice concentrate

Combine ingredients in a blender, and blend until smooth. Pour into chilled glasses and serve immediately.

Nutrition per 1-cup serving: 200 calories, 4 milligrams cholesterol, 177 milligrams sodium, trace total fat, 41 grams total carbohydrates, 5 grams dietary fiber, 12 grams protein, 26 grams total sugars

By Mayo Clinic Health System staff.