Nutrition Before a Half Marathon

Chris Park , On October 13, 2022


What to eat before a half-marathon

Proper nutrition for a half-marathon is the second most important task after training. Proper nutrition for a half-marathon includes the months lead up to the event as well as eating right the day of the half-marathon to help perform your best. Finally, the right half-marathon meal plan after your event will determine how your body recovers. There is a lot of debate about how and what to eat before a half-marathon. While marathon meal plans can be determined by individual tastes, the fundamentals of eating for endurance involves the right amount of calories, and the right macro nutrient balance. Here are a few suggestions about nutrition for running a half-marathon.

Nutrition in the weeks leading up to a half-marathon

Even though the half-marathon is on one set day, nutrition preparation for a half-marathon takes months. And the day prior to the half-marathon is the day you absolutely want to get your diet on point. In fact, it is said that nutrition the week prior to the race is more important than the day of the actual half-marathon. This is because the source of calories, macronutrients and micronutrients, all determine how you perform the day of the race. A nutritionally depleted body cannot perform the day of the marathon despite the best meal or hydration on that particular day. Nutritional deficiencies, particularly of macrominerals can build over a period of time and take time to correct. So, properly eating for the half-marathon should be an ongoing process that is highly critical a week before the race. Eat all 8 types protein, and vegetables for a half-marathon diet. Supplement this with electrolyte-based hydration a week before, because just like nutrients, hydration also should improve on a daily basis.

Diet the day before a half-marathon

The advice that is most commonly given is that a balanced meal, easy to digest, rich in the best carbohydrates, protein and fiber is probably the best pre-marathon diet. An ideal menu item on a half-marathon diet plan includes a easy salmon recipe with potato, and spinach. Of course, one can substitute meat for a vegetarian patty and add vegetables to taste. The idea is that your ideal pre-marathon meal plan should have enough calories coming from mixed sources of macronutrients- protein, carbohydrates and fat. The meal should also be rich in electrolytes including sodium, magnesium and potassium. There are many athletes who eat the same food all week before a marathon “just to get it right” and stay on track with their diet. A side of apples, bananas or freshly squeezed orange juice can significantly help electrolyte intake which is key to building your electrolyte levels up prior to the marathon.

Eating the day of the half-marathon

As expected, eating right the day of the race is critical. The morning of the race an ideal half-marathon diet plan should look something like this:

Meal 1: The first meal in the morning should be kept light but should have enough calories to sustain yourself at least for an hour (or 45-60 minutes). A carb rich meal is a good idea. For examples: a bagel with cheese and jelly, peanut butter sandwich, egg white sandwich, etc. Some Carbohydrates during the race are the easiest source of energy. Avoiding a protein rich meal as fuel prior to the half-marathon race has its advantages because protein takes longer to digest and it is harder for your body to use amino acids quickly for energy than carbohydrates. Do not overeat prior to your race.

Meal 2: Easy on-the-go eatables such as bananas, graham crackers, jelly beans, sugar blocks are excellent sources of energy. Some carbohydrate rich gels are also good choices since they can be easily absorbed from the gut. Normally, muscles and liver contain enough glycogen (about 1800-2200 calories worth of) to last your race but as glycogen gets depleted and after about 60 minutes of continuous activity, some refueling is needed.

Hydration: During the race energy must be obtained on the go. An energy drink with electrolytes is great fuel for an endurance event like a half-marathon. Ideally, drinks should have some sugar as an instant source of energy. Sugar free drinks do not sustain a marathon endurance run. Some athletes use about 10-15 g of carbs per 45-50 minutes of activity. If used correctly with the right blend of electrolytes, that amount can be cut down (for those who are sugar conscious). Hydration is not just a source of water but also for some nutrition as well as electrolytes. Sugar in the energy drink should not be > 10 grams per 12 fl. oz of water, to keep the osmolality of the solution low. As dehydration ensues, the higher osmolality in the blood allows the water and electrolytes to be absorbed from the stomach quicker. A very high sugar content (>20 grams /8 fl. oz as in common sports drinks) prevents this and leads to nausea. Your drink should be rich in magnesium, potassium and have a balanced amount of sodium (at least 200 mg or 400 mg of sodium chloride) since sodium is the principal electrolyte lost in sweat. Sodium deficits in some marathon runners may be up to 1-1.5 grams per race, but the replenishment can be gradual, during the race and during the recovery.

Drinking enough liquids allows blood volume to be maintained and electrolyte balance to be proper. It also prevents cramping, low blood pressure and overt dehydration.

Hyponatremia Definition: A low blood sodium level that can develop when the body is losing salt through sweat but only water with no salt is being ingested with no sodium replenishment. This causes a blood-sodium imbalance. When the body is dehydrated, vasopressin – an anti-diuretic hormone is released from the brain that causes water retention. To prevent this condition from developing drink an electrolyte drink when performing a strenuous activity that lasts more than 30-40 minutes.

Drinking 8-10 fl. oz of electrolyte water, every 20 minutes of activity/running at a moderate pace is the minimum that we recommend. If it is hot or you tend to sweat more, a higher rate may be needed. One should aim to at least consume 16 fl. oz or roughly half a liter of liquid per 30-40 minutes of activity in this setting. Magnesium allows potassium to be retained in the body and muscles to contract efficiently without cramping. Sodium and water allow blood perfusion to be maintained. Supplement that with some calories from simple sugars, and you have the right fuel to ensure you hit a PR on your next half-marathon.

Chris Park

Chris Park is a board-certified sports nutritionist, registered dietitian and former college rugby player. Chris loves strength training and pushing his body to the limit, which comes in handy when working with professional athletes and designing their nutritional needs. Chris also enjoys helping others by writing about nutrition.