You've spent months training for your upcoming race: diligently logging miles on the road and treadmill alike. So what could keep you from having an excellent race day? Nutrition. What you eat before, during, and after a marathon can make or break your performance. So here are some guidelines to make sure your eating habits aren't counterproductive to the time you've spent in physical training. You can consider them "the Ten Commandments of Marathon Fueling."

2010 Antarctica Marathon participants. Photo courtesy of www.marathontours.com/

BEFORE YOUR EVENT:
1. Prioritize carbohydrates in your diet plan. Carbohydrates are the primary source of fuel for intense exercise. The body stores dietary carbohydrate in the form of glycogen in the muscles and liver. These stores are efficiently converted to energy to fuel a marathon, or any endurance event lasting more than 60-90 minutes. To maximize their glycogen stores, athletes often increase their intake of carbohydrates to comprise 70% of their diet three days prior to an endurance event. This time-honored tradition is known as "Carb Loading." That's not to say you have license to camp out at your local doughnut store--carbohydrate choices should be unrefined and unprocessed. Refined and processed carbohydrates can lead to weight gain.

2. Familiarize yourself with the glycemic indexes of foods. The glycemic index, or GI, ranks carbohydrates based on the effect they will have on our blood glucose levels. High GI rankings (70 and above) cause a spike in blood sugar, followed by an inevitable crash. This leaves you feeling jittery at first and then sluggish--not a good combination for anyone, let alone runners. Low GI foods (55 and under) deliver glucose into the blood stream slowly, keeping your body balanced. You'll feel more satiated between meals if you eat foods with moderate to low glycemic indexes. Oatmeal, whole wheat breads and pastas, brown rice, fruits and vegetables are all ideal choices.

3. Allow enough time for digestion of food before an endurance event. Foods that loiter in your stomach can cause nausea or diarrhea during your run. Eating a large meal three to four hours before an event will ensure enough time for partial digestion, absorption, and relatively complete emptying of the stomach. A smaller meal needs only two to three hours to digest. A liquid meal may take two to three hours, and a small snack will take less than an hour; experiment to find which method works best for you.

Don't be tempted to skip a pre-race meal to avoid digestions mishaps. A pre-race meal is your last chance to make final additions to your muscle glycogen stores. Furthermore, it can prevent low blood sugar--the culprit behind light headedness, dizzy spells, fatigue, and blurred vision during races. A pre-exercise meal should be high in carbohydrates, not greasy, and easily digested (not a lot of fiber). Limit high-fat foods, as they delay stomach-emptying time and take longer to digest.

DURING YOUR EVENT:
4. Supplement your body energy stores throughout the race. At most, your body can store enough fuel to last for 60-90 minutes of continuous exercise. But marathons can last for two and a half hours to four hours or more. That means you'll need to continue your intake of carbohydrates throughout an event to maintain normal blood sugar levels and keep your muscles well-fueled. Many find bananas, sports bars, or sport gels to be ideal choices. However, don't overdo it. Too much food or liquid may land you with stomach cramps or indigestion.

5. Hydration is key. Athletes often find carbohydrate-containing fluid sources (Gatorade, Powerade) to be an ideal way to replenish exhausted energy stores. This "kills two birds with one stone" because in addition to replacing carbohydrates, it is important to stay well hydrated during an event. If you find yourself feeling thirsty, chances are you are already dehydrated. So don't gage your fluid intake by thirst as it can be a misleading indicator. Athletes should take in enough fluid to replace that lost in sweat. Complications such as heat stroke or heat exhaustion may occur if an athlete does not replace lost fluid. Experts recommend drinking sips of water or sports drink every 15-20 minutes.

AFTER YOUR EVENT:
6. Replace lost electrolytes. Eating a small amount of food within 20 minutes after running helps to replace muscle fuel and rebuild your glycogen stores.  Salty foods as well as potassium-rich fruits (like bananas and oranges) can help to replace lost electrolytes.

7. Give your body the protein it needs to repair damaged muscles. You can meet your body's protein needs by eating a balanced diet of adequate caloric intake. Expensive protein supplements are unnecessary. Instead, focus on dairy, meats, and fish (or soy/legumes/beans for vegetarians).

8. Continue to hydrate. Frequent urination is a sign that you're taking in enough fluid.

LAST WORDS OF ADVICE:
9. Unsaturated fat trumps saturated and trans fat in keeping your arteries clog-free. There are several types of fats found in food: polyunsaturated, monounsaturated, saturated and trans fat. While research studies have shown no performance gains associated with any type of fat intake before, during or after a workout, it's unrealistic to eliminate them completely from your diet. An athlete will usually aim to have 15-25% of his/her diet come from fat. When included, rich sources of poly or monounsaturated fats (nuts, seeds, or plant oils) are preferable to saturated and trans fats (fatty meats, whole-milk dairy products, or fried foods). Saturated and trans fats raise blood cholesterol levels, putting you at risk for coronary heart disease, while unsaturated fats work to rid the body of deposited cholesterol.

10. Find what works for you and stick with it. Often times marathon spectators will be handing out food. Be wary of trying anything new on race day. Avoid the risk of abdominal discomfort by eating only foods that you have tried before and have served you well during long training runs.

Christine Gary