Healthy nutrition is important for runners before, during and after a workout. It's important before a run because it provides you with the fuel to carry out the particular task.
Your muscles contain a limited amount of glycogen -- a type of glucose that is your body's most readily available source of energy. If you've been eating a regular diet consisting primarily of carbohydrates with a lesser amount of protein, your muscles and liver will contain about 2,000 calories that are ready to burn [source: Latta]. That's enough to get most people through about 20 miles of running. Keep in mind, however, that eating right before a run might not be the best plan.
Time your meals a couple hours before a workout. If you must eat closer to the time of your run, then make it a light meal -- perhaps a bagel, yogurt and a cup of fruit juice. Proteins and fats are particularly hard for your body to digest. It may take as long as five hours for them to move from your stomach, farther into the digestive system. For that reason, it's best to avoid heavy foods immediately before heading out to run [source: Run The Planet].
During a run, hydration is the core component of good nutrition. Without water your body can't work optimally. If you need fuel in the form of an energy bar, gel or other highly soluble form of carbohydrate, water will help facilitate digestion. Avoid caffeine, however. Caffeine dehydrates your body at a time when it needs just the opposite [source: Run The Planet]. Sugary items also contribute to intestinal distress. Always experiment with sports drinks, fruits (like bananas and oranges) and energy bars before using them in a race. It's very common for runners to miss their goal on race day by trying something new and discovering that their body doesn't react well to it.
Eating may not sound good following a tough workout, but replenishing your body is very important. Think of your body's cells as sponges. Those cells are more open to nourishment in the half-hour following a run than at any other time [source: Shea].
Ignoring that window means your body won't rebuild as fast as it otherwise could.
You'll want healthy carbohydrates and protein. The ratio of carbohydrates and protein should be about 4-to-1. A good example might be crackers covered with peanut butter [source: Shea]. The antioxidant properties in fruits will also help replenish your body.