Marathon Diet: Avoiding Nutrient Deficiencies

Marathon Diet: Avoiding Nutrient Deficiencies

Ben Connelly

Most runners know nutrition matters. But oftentimes, runners focus on macronutrients (carbs, protein, and fat), while neglecting micronutrients. It turns out, micronutrients are far more important. As long as your diet is reasonably balanced between carbohydrates, protein, and fat, you do not need to obsess over macronutrient ratios. But you should pay attention to your micronutrient intake. 

Vitamins and minerals play an essential role in health for every human. But athletes, whose training places great demands on their bodies, need even more of these critical micronutrients. And athletes are more likely to notice the effects of a deficiency, which can dramatically hamper their performance. Marathon runners are no different. In fact, marathon training places such great demands on the body that marathoners need to pay more attention to their diet than most other runners.

Can I Just Take a Vitamin?

Some experts debate how much multivitamins really work. Multivitamins do not hurt. Specific vitamin and mineral supplements (for example, a Vitamin D pill) can have beneficial effects. They can help correct serious deficiencies. (Iron supplements are often necessary to correct anemia, for example.) But every person should strive to get vitamins and minerals from their diet. Marathon runners especially should not assume that a multivitamin covers their needs. (In most cases, you will absorb micronutrients better from food than from a pill.)

With a properly balanced diet (and sun exposure), you can absorb enough of each essential vitamin and mineral without any supplements (except when genetic factors predispose you to deficiencies – meaning your body cannot absorb certain nutrients as well as another person). 

Important micronutrients include:

  • Vitamins A, B, C, D, E, and K 
  • Calcium, magnesium, zinc, iron, manganese, sodium, potassium, and selenium

(Note: Vitamin D comes from sunlight. To avoid a deficiency, you need sun exposure.)

Nutrient-Dense Foods:

Instead of obsessing over each vitamin and mineral, focus on eating a varied diet of nutrient-dense foods. Mainly vegetables. I recommend eating several different vegetables every single day, including dark, leafy greens (spinach, kale, arugula, etc.). You could eat a large salad with spinach every single day. Rotate through different vegetables each week. 

Vegetarians and vegans will also have to work a little harder, because meat is one of the best sources for B vitamins, iron, and other nutrients. Vegans may need to take supplements to avoid deficiencies. 

A partial list of nutrient-dense foods:

  • Meat: chicken, beef, lamb, etc.
  • Vegetables: dark greens, avocados, broccoli, carrots, tomatoes, green beans, peppers, onions, asparagus, Brussel sprouts, radishes, etc.
  • Nuts: Brazil nuts, almonds, etc.
  • Eggs: Despite the myth, eggs are not unhealthy. They are one of the best foods you can eat.
  • Beans
  • Potatoes: Potatoes actually contain small quantities of almost every vitamin and mineral you need.
  • Fish: salmon, tuna, cod, etc.
  • Fruit: berries, cherries, citrus fruits, etc.


During high-mileage days and the dark weeks of winter, runners should focus on eating a wide variety of nutrient-dense foods. Nutrient deficiencies can seriously impact training and race performance. Proper nutrition maximizes both training and recovery. The best strategy is to eat a varied diet, rich in vegetables. 

By paying a little attention to your nutrient intake, you can start to spot potential deficiencies and correct for them. For example, if you think you may be low in vitamin A, start eating carrots, spinach, and sweet potatoes. If you think you need vitamin K, try spinach and broccoli. Some quick Google research can help you identify areas for improvement. And it can help you find nutritious foods that you enjoy.

Next week, I plan to talk about a few common misconceptions about certain micronutrients. When it comes to sodium and iron, many runners have the wrong idea about what constitutes too much or too little. Stay tuned.


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“Eat your vegetables! Marathon nutrition is not all about carbs. Check out our latest blog post for more on why you need to pay more attention to micronutrients, than you do to macronutrients.”

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