Nutrition Tips for Marathon Virgins and Veterans

While it may seem that burning large numbers of calories during training justifies eating a diet high in junk food, runners are not invulnerable to the consequences of poor dietary habits. Maintaining health and reducing risk of chronic disease requires healthy dietary habits, regardless of the daily mileage you rack up.

A recent study published in the British Medical Journal assessed 42 Boston-marathon qualifiers, who were compared to their less-active spouses. Overall the runners had 11 percent lower body mass index, 26 percent lower triglyceride levels and 13 percent lower cholesterol levels, compared to their partners. While that sounds promising, the researchers found that the improved cardiovascular risk profile of the runners did not reduce their risk of heart disease. This showed that while exercise improved their cardiovascular risk profile, it did not inhibit the progression of carotid atherosclerosis associated with age and cardiovascular risk factors.

The findings from the new study don't discount the benefits of exercise, but they do suggest that exercise alone may not improve long-term health outcomes. In order to most effectively decrease your risk of heart disease and other chronic diseases, healthy dietary habits are essential. The good news for marathoners is that a healthy diet not only decreases risk of heart disease, but it's also associated with enhanced physical performance.

Whether you are a marathon virgin or veteran, your health and performance on race day are directly linked with what you put in your body. In order to run fast and recover quickly, use these tips to ensure that the body is well-fueled and properly hydrated:

1. Eat enough calories.

Runners who put in a lot of daily miles have high-energy needs. Studies show that maintaining an adequate intake of energy is essential to avoid compromised performance and immune function, as well as increased risk of injury and chronic fatigue. Energy needs are very individualized and depend on an athlete's body size and composition, gender, age, and training regimen.

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2. Consume plenty of carbohydrates.

Eating enough carbohydrates during the months of training is critical for performing your best. Carbohydrates are the body's primary source of energy, and studies show they help replace the muscle glycogen lost during endurance activity. The body converts glucose from carbohydrates into glycogen that is stored in the muscles and liver. High muscle glycogen levels at the start of a workout play a role in the intensity and duration of an exercise session.

The body's need for carbohydrates depends on the duration and intensity of the workout. On a day of moderate-endurance exercise, which is less than an hour, aim to consume 5 to 7 grams of carbohydrates per kilogram of body weight. For an athlete who weighs 155 pounds, this 5 to 7 gram recommendation translates to 350 to 490 grams of carbohydrates per day. On days of high-volume training, an individual should consume more carbohydrates -- approximately 7 to 10 grams per kilogram of body weight. For a 155-pound person, that translates to 490 to 700 grams of carbohydrates each day.

3. Choose your carbohydrates wisely.

A high carbohydrate intake does not warrant the consumption of bagels, muffins and grains that are filled with refined carbohydrates. Get the most bang for your carbs by choosing 100 percent whole grain options that provide a rich source of B-vitamins, iron, zinc and fiber. Smart carbohydrate sources include fruits, vegetables and grains that are 100 percent whole, such as brown rice, oatmeal, popcorn and quinoa.

To meet carbohydrate recommendations, athletes who consume approximately 2,600 calories a day should aim for four servings of fruits, seven servings of vegetables, nine servings of whole grains, one serving of beans and three servings of milk each day.

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4. Pair spinach with tomatoes.

Iron is a critical mineral for athletes, particularly female athletes, because it promotes respiratory function during physical activity and helps transport oxygen to the muscle. Traditional foods that are rich in iron include fish, poultry and meat, but there are plants -- such as spinach, broccoli and collard greens -- that provide the mineral as well. Since the bioavailability of iron is lower in plants compared to animal products, it can be enhanced when paired with foods rich in vitamin C, such as tomatoes and peppers.

5. Rely less on cows.

Instead of associating protein with hamburgers and steak, consider the benefits of plant-based sources of protein, such as nuts, beans, tofu, edamame and quinoa. Try reducing your intake of meat, and incorporate more into your snacks and meals. A diet high in animal products is associated with a higher consumption of harmful nutrients, such as saturated fat and cholesterol. A recent meta-analysis found that vegetarian diets are associated with lower systolic and diastolic blood pressure, which in turn lowers risk of heart disease.

Aim for consuming 1.2 to 1.4 grams of protein per kilogram of body weight each day. Meet your body's protein needs with lean sources of meat such as skinless chicken, salmon and eggs, as well as a variety of plant-based foods. Most plants do not contain all the essential amino acids (with the exception of quinoa and soy) but eating a variety of plant-based sources of protein throughout the day will provide all the amino acids needed for proper growth and repair.

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6. Choose rich sources of healthy fats.

Studies show that many athletes choose to follow a low-fat diet. Rather than focusing on consuming foods low in fat, try incorporating full-fat foods that supply heart-healthy fats. Examples of healthy, unsaturated fats include olive oil, canola oil, avocadoes, nuts and seeds. Incorporating healthy fats in your diet and avoiding sources of saturated fat, such as coconut and palm oil, whole-fat dairy products, and baked goods helps promote heart health. Get in the habit of cooking with olive or canola oil instead of butter, and try snacking on trail mix instead of pop-tarts. As a general guide, endurance athletes training for a marathon should consume 2.0 grams of fats per kilogram of body weight.

7. Maintain hydration.

Dehydration is associated with poor physical performance and risk of weakness, cramps, headaches and dizziness. In order to avoid dehydration, it's important to consume large amounts of water throughout the day. When running for more than two hours, it's imperative that your fluids contain sodium to replace lost electrolytes. Research also suggests that runners should ingest 13 to 26 ounces of fluids for every hour of exercise. When running for longer than an hour, make sure your beverage contains 6 to 8 percent carbohydrates, which will help stabilize blood glucose levels.

8. Refuel within one to two hours of exercise.

The window of time for optimal replacement of energy stores and the prevention of protein breakdown is within one to two hours of working out. Get in the habit of consuming a combination of carbohydrates and protein immediately after exercise. Examples include eight ounces of chocolate milk, a smoothie with whey protein or yogurt. Pairing protein with carbohydrates has been found to stimulate muscle glycogen synthesis, which is important for adequate recovery.

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9. Carb-load 24 to 36 hours pre-race.

The most effective time to load up on carbohydrates is 24 to 36 hours before a race. Studies show it boosts performance and may reduce fatigue associated with glycogen depletion.

A 2011 study from the International Journal of Sports Medicine assessed the effect of pre-race carbohydrate loading on marathoner runners. The researchers found that ingesting carbohydrates the day before the race was a significant and independent predictor of running speed. Compared to those with a low carbohydrate intake, runners who consumed more than seven grams of carbohydrates per kilogram of body weight the day before the race ran faster and maintained their speed to a great extent.

Applying these nutritious tips to your training regimen will not only boost your performance on race day, but it will also promote long-term health by reducing your risk of chronic disease. Happy running!

Brigid Titgemeier, Nutrition Assistant at the Cleveland Clinic Wellness Institute, contributed to this article.

Kristin Kirkpatrick, MS, RD, LD, is the manager of Wellness Nutrition Services at the Cleveland Clinic Wellness Institute. She is an experienced presenter, an award-winning dietitian, an author and a regular television guest on both local and national shows, as well a contributor to several national magazines and newspapers. The Huffington Post recently named Kristin "one of 25 diet and nutrition experts you need to follow on Twitter." Kirkpatrick's career began in Washington, D.C., lobbying for Medical Nutrition Therapy reform, and from there she went on to become the Regional Coordinator of the National Heart, Lung and Blood Institute's Hearts N Parks program in Maryland. Follow her on Twitter at @KristinKirkpat.