Eat a rainbow. Many runners' diets take on a brown hue because of the idea that carbo-loading on pastas fuels performance. And, while whole grains are admittedly good for distance runners, getting colorful is, too. During training, a distance runner's diet should have a brown foundation (all those healthful whole grains), topped with generous portions of dark greens, such as leafy spinach -- a source of iron, calcium, potassium, beta carotene, folate and vitamins C, D and K [source: USDA]. It's also important to include brightly colored fresh produce, such as sweet red peppers or mangoes, both of which are rich in minerals and vitamins C and A [source: WebMD]. Selecting colors rather than beige-tones usually means foods have more nutrients per calorie [source: Morris].
Following this "color prescription" also helps distribute calories between whole grains, fruits and vegetables, and fats and protein. It's an easy way to see how a distance runner's daily food plan is distributing the big three: carbohydrates, fats and proteins. A runner should get the lion's share of his or her calories (about 60 percent) from carbohydrates [source: Pfitzinger]. The next largest chunk of calories, about 25 percent, should come from fats, followed by protein at about 15 percent [source: Higdon].
It's also a good idea to follow this rule of thumb: Don't eat foods that can be handed through your car window. Although highly processed foods offer the calories your body needs, they lack the vitamins, minerals and other nutrients you'll find in ingredients closer to their original state. High-nutrient whole foods will fuel your body for the long haul [source: Morris].
Of course, when it is time for the big race, don't stuff yourself with a pre-run meal -- even if it is the night before. It will take an entire day for this food to be processed by your body and turned into fuel, so your carb-rich pasta dinner or your midnight snack will still be bouncing around in your belly when the starting gun fires the next morning. Instead, consider eating a number of small meals the day before the race, then weaning yourself from food by early evening. It may keep you from tossing your cookies at mile-marker three [source: Galloway].
All this talk of eat-this-then-not-now may have you turning to supplements for comfort. While the idea of getting your protein from a bar or your iron from a pill is tempting, it's not a good substitute for a runner's well-balanced diet. Your body doesn't absorb supplements in powder or pill form with the same efficiency as it does real foods [source: MayoClinic]. You can make water "wetter," though. We'll fill you in on the next page.