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Nutrition 101

What to Eat and Drink Before a Marathon

What to Eat and Drink Before a Marathon

7-continent marathoner Mable Wong shares her nutrition tips for running a marathon.

Many marathoners are curious about their nutrition plan prior, during and after the race. Having run a marathon on all 7 continents, I've learned a lot about what the body needs to perform! I'd like to share some tips on how to properly sustain and hydrate yourself for peak performance on the big day.

So you’ve dedicated the past 4 months or so training for the marathon. You’re physically and mentally primed for the big day. Are you nutritionally prepared? Performance on race day depends on your training and fueling strategy. Proper nutrition will help your performance and lend to a speedy recovery.  Here, I'll explore what could possibly go “wrong” and how to avoid these unfavorable situations.


The main fuel for your muscles and brain (the most important muscle!) comes from carbohydrates in your diet. Carbohydrates are stored in your body as glycogen.“Hitting the wall”, feared by many endurance athletes, results from depleted glycogen stores in the muscles and liver. Intense exercise, such as running a marathon, relies primarily on glycogen for fuel, as the body can not break down fat as efficiently. So endurance athletes should steer clear of the low-carb diet trends. 


On average a trained athlete can store enough glycogen for about 20 miles of running. It is important to properly load up on carbohydrates pre-race and maintain your fuel stores throughout the race to avoid the dreaded “wall”. 

Ideally you should practice carb loading at least 6 weeks before the marathon to see what works best for you. Record what you ate, how it was prepared, the timing of the meal, and how you felt.  This will help you devise a plan as race day nears. If travelling to the race, be prepared with snack mixes and look in advance at dining options in the area.  

Some general guidelines for carbohydrate loading are below:

  • 2 – 3 days before the marathon: Your daily carbohydrate intake should be 85 – 95% of consumed calories. Sports dietitian Monique Ryan recommends 4 grams of carbohydrate for each pound of body weight. Choose whole grains and fiber rich foods, when available. Remember to balance your carb options. Too much fruit can cause diarrhea and too many refined carbs can lead to constipation. Avoid alcohol and caffeine as these will dehydrate you. You’ll know if you carb loaded properly if you gain 2 – 4 pounds. This is water weight since every 30g glycogen stores about 3 oz of water. 
  • 24 hours before: Don’t overdo it.You don’t want to wake up on race day full from the night before. Choose foods lower in fiber to avoid any gastrointestinal distress, keeping in mind what works best for you. I prefer small meals high in carbs throughout the day before and try to have an early dinner before going to bed early. I typically wake up 3 hours before the race start time and eat about 300 calories and hydrate.  
  • During the race: It’s best to consume 100 calories (less than 30g carbohydrate) every 30 – 45 minutes of running. What works best for me is an energy “gel” with both protein and carbs that helps restore electrolytes and maintain my glycogen stores for the remainder of the race. The protein in the gel also may increase time to exhaustion and helps with your recovery. Here’s a homemade recipe that you can make and freeze in a plastic sealed bag before the race:

1 ½ tsp. molasses
½ tbsp. Coconut water
¼ oz soy protein isolate
2 tsp. brown rice syrup
⅛ oz dried chia seed
Pinch salt


The major causes of gastrointestinal (GI) distress during a race include strenuous exercise, dehydration, and the rate of gastric emptying. Vomiting usually occurs during a marathon because less blood travels to the gut. Gastric emptying rate is greatly influenced by the type of foods consumed, more specifically, the protein-fat-carb ratio. While running, less blood travels to the gut, so it does not work as efficiently. Here are some general pre-race guidelines:

15 to 30 minutes before start
- Calories - no more than 150
- Fiber - no more than 1g per serving
- Fat - no more than 6g per serving
- Examples: apple sauce; 6oz nonfat yogurt; glass of non-fat chocolate milk

30 to 60 minutes before start
- Calories - no more than 300
- Fiber - no more than 2g per serving
- Fat - no more than 6g per serving
- Examples: bowl of cereal with banana; toast with jam and glass of non-fat milk

Also keep in mind that certain foods may irritate the digestive tract more than others, causing “runner’s trots” (gas/bloating, diarrhea, constipation, or intestinal cramping). Some trigger foods to avoid before a big event include carbonated drinks, mint, caffeine, beans, and dairy. During the race, consuming more than 30 – 60g carbohydrate per hour may cause stomach cramps (note a 4 oz. fruit juice contains an average of 15g carbs). Try to steer clear from fructose, sorbitol, and raffinose, also found to irritate the gut in runners.

Lastly, avoid taking aspirin before such an event because it increases intestinal permeability. Combined with vigorous exercise, aspirin increases the chance of allergen absorption in the gut, which in turn may increase the chance of food dependent exercise induced anaphylaxis (FDEIA). This condition is very rare, but it is best to steer clear from popular trigger foods such as wheat, rye, barley, shellfish, nuts, dairy, and alcohol. 


Being properly hydrated will also enhance your performance on race day. Thirst is not a reliable indicator as it’s triggered when you’re already 5% dehydrated. Your heart rate increases about 3-5 beats/minute for every 1% body weight loss from dehydration (which also increases blood pressure). This means that your heart is working harder, wasting valuable resources, and possibly increasing glycogen oxidation. 

A general rule of thumb is to drink 16 ounces of water an hour before the race, then 4-6 ounces every 20 minutes after you begin running. When you reach over 90 minutes of activity, be sure to consume a sports drink with added electrolytes to avoid hyponatremia (a condition caused by a loss of sodium from sweat and increased water intake). Most important, pay attention to your body during the race. Anything that reduces the evaporation of sweat (humidity, body dehydration, etc.) can lead to heat illness or exercise induced hyperthermia. 

new york city marathon, nutrition advice, marathon tips, 7 continent marathoners

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