What is a marathon runner diet? Anyone who has ever trained for a race, joined a track team, or ran casually knows that running requires a lot of extra work from your body. Your lungs, heart, and muscles are all working much harder, requiring more nutrients and energy. Many times, nutrition for athletic events, like the marathon, are focused on macronutrients. But micronutrients are just as important! Micronutrients are needed for your body to use the macronutrients properly, repairing muscles and giving you energy during a run. It’s crucial to make sure you are replenishing everything your body is using! That means both micros and macros. It is important eat an adequate amount of nutrients during marathon training for three key reasons.

Three Reasons for the Marathon Runner’s Diet:

  • Performance:

    • Good nutrition will help you cross the finish line at the 26.2-mile mark. When we fuel our bodies with nutrient dense foods our bodies are able to run their best and can recover more quickly. This is true for a race or training run of any distance, but is especially important with the increased stress that marathons bring.
  • Energy Maintenance:

    • This is especially important for marathon runners because running can take a toll on your body and you want to maintain your usual energy level. Marathon mileage requires a lot of energy, so to ensure that you have enough, it is crucial to eat plenty of complex carbohydrates, healthy fats and protein. Especially at the marathon distance, maintaining energy can help prevent “bonking” or “hitting the wall” both in training runs and during the race.
  • Prevent Chronic Diseases:

    • In general, eating a healthy diet with adequate amounts of all the nutrients helps prevent the development of heart disease, cancer, and diabetes. We’re focusing more on running and performance in this blog, so we won’t talk much about chronic diseases.

marathon runner diet

Important Nutrients for the Marathon Runner:

It can be really hard to decipher exactly what to increase in your diet during marathon training! One source will tell you that X is more important, while another would say that you should eat all Y. There are a lot of factors that go into creating the “ideal” intake and they vary greatly from person-to-person. However, there are some common things that can help maintain your health and energy while avoiding injury.

Here are our top four things to keep an eye on:

  • Calcium:

    • Calcium is important for the maintenance of strong bones and muscle growth, which is very important when training for a marathon. Calcium deficiency can cause running to weaken your bones. Sources of calcium include dairy products, leafy green and vegetables.
  • Iron:

    • Iron is required for the production of hemoglobin, which is responsible for carrying oxygen from the lungs to the muscles. With aerobic activity like running, your muscles need more oxygen, so iron is a very important nutrient to prevent fatigue. Individuals deficient in iron often feel very tired, even when they get enough sleep and are not doing strenuous workouts. Some good sources of iron are red meat, fish, and fortified cereals. Female athletes are at more of a risk for iron deficiency because of blood lost during menstruation.
  • Iodine:

    • While it doesn’t seem to directly impact running performance, it is clear that exercise impacts iodine levels. Iodine is lost through sweat so it is important to replenish what is lost for proper thyroid function, which controls hormone production, metabolism, and energy output. Iodine is naturally found in seafood, but in the US, table salt is typically fortified with iodine, but you should check the label to make sure.
  • Vitamin E:

    • Vitamin E acts as an antioxidant, which counteracts the effects of oxidative stress on the body. It has been proven that exercise can increase oxidation, which increases the need for antioxidants. Oxidative stress can play a role in muscle stiffness or soreness, so vitamin E can help reduce soreness after tough workouts or long runs. Some food sources of vitamin E include nuts and seeds.


If you would like to make sure you are getting all the nutrients you need for optimal marathon performance, call 301-474-2499 to make an appointment with our sports dietitian


Blog written by Haley Kappey, University of Maryland Student and RBA Nutrition Intern

Reviewed and approved by Rebecca Bitzer, MS, RD, LD

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Rebecca Bitzer loves to empower Registered Dietitian Nutritionists (RDNs) and their clients.  Co-author of Welcome to the Rebelution: Seven steps to the nutrition counseling practice of your dreams and  Taste the Sweet Rebellion: Rebel against dieting.