For access to all of our training, gear, and race coverage, plus exclusive training plans, FinisherPix photos, event discounts, and GPS apps, sign up for Outside+.
Some minerals are especially important for endurance athletes.
Written by: Matt Fitzgerald
Got (enough) minerals? There are 22 essential minerals that we all must include regularly in our diet to ensure optimal health, regardless of how much we exercise. Add in long marathon training runs and a handful of minerals become especially important. Specifically, runners need to be certain they meet their calcium, iron, sodium, and zinc needs in order to support peak endurance performance.
When you think of calcium, you probably think of bone health. While it’s true that calcium is vital for bone health, it plays an equally important role in muscle contraction and even affects fat storage in the body. That means you need enough calcium in your diet to develop stronger bones in response to training stress, get maximum performance out of your muscles, and maintain a lean body composition. But chances are you’re not getting enough calcium. The recommended daily intake of calcium is 1,000 to 1,300 mg. The average adult consumes only 500 to 700 mg daily.
You can avoid a calcium deficiency by consuming three servings of low-fat or non-fat dairy foods per day (an 8-ounce glass of milk equals one serving). But research suggests that calcium supplements are even more effective than dairy foods in maintaining bone density.
Iron is critical to the formation of red blood cells, which carry oxygen to the working muscles during exercise. Inadequate dietary iron intake causes anemia, which is characterized by persistent fatigue and is a real performance killer in endurance athletes.
Anemia is common among runners. Scientists are not certain why, but there is some evidence that one or more aspects of exercise stress destroys red blood cells and thereby increases iron needs.
The recommended daily iron intake is 10 grams per day for men and 15 grams for pre-menopausal women. Iron deficiency is easily avoided through adequate intake of iron-rich foods including tuna, chicken, and beef. Vegetarians and light meat eaters may need to supplement, but consult your doctor before taking an iron supplement since excessive iron intake is toxic. In addition, all runners should have their iron levels tested annually by a physician.
Sodium is an electrolyte mineral, meaning it conveys electrical signals—including those that cause your muscles to contract—throughout the body. Large amounts of sodium are lost in sweat during exercise, so runners need more sodium than non-athletes. But this doesn’t mean you have to go out of your way to add salt to your diet. Non-athletes require only about 500 mg of sodium daily. The average American consumes seven times that amount. Chronic sodium deficiency is unheard of even among the hardest-training endurance athletes.
It is, however, a good idea to consume sodium during prolonged exercise—especially in the heat. Doing so helps prevent blood volume from decreasing as a result of sweat losses, and this in turn helps preserve cardiac efficiency. Sports drinks such as Accelerade and Cytomax are formulated to provide the optimal amount of sodium during exercise.
Zinc is present in all of the body’s enzymes and it plays an essential role in gene expression, which is the source of many positive fitness adaptations to exercise training. A number of studies have demonstrated the importance of adequate zinc intake to exercise performance. For example, a 2005 study published in the American Journal of Clinical Nutrition reported that a low-zinc diet increased heart rate and respiratory stress during exercise in a group of volunteers. That’s because zinc is a critical component of an enzyme that helps remove carbon dioxide from the blood.
The recommended daily intake of zinc is 8 mg for women and 11 mg for men. But because some zinc is lost in sweat, athletes may need slightly more. The best food sources of zinc are beans, nuts, and whole grains.
Check out Matt’s latest book, RUN: The Mind-Body Method of Running by Feel.