By Emily Bailey
Hydration is a key to optimal performance and recovery, and that’s true regardless of the season. In fact, impaired performance can result from even a 2% loss of water weight (3 pounds for a 150-pound athlete). Hydration is about more than replacing fluids, however. It is also about your intake of electrolytes. Many athletes turn to sports drinks or electrolyte tablets to replace these important minerals. But did you know that you can get many of your electrolyte needs met through foods? This is especially encouraging if you are not a fan of sports drinks. Here is a quick reminder of the roles of specific electrolytes in exercise, as well as tips for adding electrolyte-rich foods to your meal plan.
Electrolytes and Exercise
Electrolytes are minerals, including sodium, potassium, chloride, magnesium and calcium. The most concentrated electrolytes that are lost in sweat are sodium and chloride, and to a lesser extent, potassium, magnesium and calcium. These electrolytes are very closely regulated by the body and across the cells to maintain many functions.
Of course, electrolytes are well known to help with hydration, which allows for improved performance. Electrolytes and food, mainly carbohydrates, facilitate the absorption of water. They allow fluids to cross the intestinal lining into the bloodstream to be carried to the tissues.
Even more important, though, is electrolytes’ role in the regulation of our heart. Electrolytes are involved in the firing of electrical charges that cause muscle contractions, including those of the heart. It’s no secret that if electrolyte levels drop too low during exercise, muscle cramps and weakness can result.
Most electrolytes are lost in sweat and urine. The amount of electrolytes someone needs is individualized based on sweat rates. Some people sweat more than others, and some athletes lose more electrolytes in their sweat than others do.
Here’s a more thorough explanation of specific electrolytes and their impact on athletic performance.
Sodium, Chloride and Performance
Those dusty crystals you feel on your skin after a long run are salt, or more accurately, sodium chloride. Typically, more salt is lost in sweat in hot and/or humid conditions, and more sodium is lost in individuals who are untrained or unacclimatized. Sodium, which is the most abundant electrolyte in your sweat, helps to facilitate communication between nerves and to regulate the amount of fluid in and around cells. Sodium is needed more than potassium to prevent muscle cramping, which runs contrary to the popular belief that potassium prevents or stops cramps (and the “eat a banana” mantra). Inadequate sodium and chloride have been associated with increased risk of heat illness, muscle cramps and hyponatremia (low levels of sodium in the bloodstream).
Which foods contain sodium and chloride?
Most foods that are good sources of sodium also contain chloride; therefore, you are receiving both electrolytes. Some foods high in these minerals are deli or cured meats, prepared bread, canned soups, pickles and many restaurant foods, such as pizza and Chinese or Mexican cuisine. If you do not regularly eat these foods, consider adding salt to your food. The amount of sodium needed per day is based on the Adequate Intake (AI) of 1,300 milligrams per day. The AI for chloride is 2.0-2.3 grams per day, depending on age, with adults aged 71 and older needing just 1.8 g/day.
Potassium and Performance
The role of potassium in exercise is related to keeping the heart healthy. If potassium levels drop too low, cell functions can be decreased, which can be very dangerous for heart health. Adequate amounts of potassium may also help decrease fatigue during exercise. (As mentioned, muscle cramping is related more to losses of sodium than potassium.) Athletes who perspire a lot or are exercising in hot or humid conditions may need more potassium.
What foods contain potassium?
There are a wide variety of foods that can help replace the body’s potassium stores. These include bananas, potatoes, flounder, oranges, tomatoes, beans and milk. The amount of potassium recommended is based on the AI of 4,700 mg/day.
Magnesium and Performance
Magnesium is involved in many metabolic process associated with exercise, such as the synthesis of protein, lipid and carbohydrate; the balance of electrolytes; and (very important) the control of neuromuscular coordination. Often people confuse muscle cramps with muscle spasms, but they are different. A muscle cramp is a contraction of a muscle that is sudden, involuntary and painful. Muscle spasms are repeated involuntary muscle contractions that come and go quickly, typically without pain. In general, more magnesium is not needed for exercisers; however, exercising in hot or humid conditions may increase magnesium needs.
What foods contain magnesium?
You can consume this electrolyte in food such as peanuts, broccoli, tofu, dark green leafy vegetables (such as spinach), tomato paste, nuts and seeds. The Recommended Dietary Allowance (RDA) of magnesium is 310-360 mg/day for women and 400-420 mg/day for men.
Calcium and Performance
We all know calcium is needed for bone health. Calcium also plays vital roles in enzyme reactions and the transmission of nerve impulses. Inside the muscle, calcium reacts with proteins to enable the muscle to contract; in fact, calcium controls the function of all types of muscles, including the heart. In hot or humid conditions, more calcium may be needed to maintain electrolyte balance and hydration. Adequate calcium intake is also associated with a healthy weight.
What foods contain calcium?
The most easily absorbed sources of calcium are found in dairy products. In a recent study in the American Journal of Clinical Nutrition, researchers reported that milk is better at hydrating than water. There are also many nondairy food sources of calcium, including almonds and dark green leafy vegetables such as kale. Women typically consume less calcium than men, so they need to pay particular attention to their intake. The RDA of calcium is 1,000-1,300 mg/day, depending on age and gender.
References:
Berchtold, M.W., Brinkmeier, H., & Müntener, M. 2000. Calcium ion in skeletal muscle: Its crucial role for muscle function, plasticity, and disease. Physiological Reviews, 80 (3), 1215-1265.
Clark, N. 2014. Nancy Clark’s Sports Nutrition Guidebook (5th ed.). Champaign, IL: Human Kinetics.
Maughan, R.J., et al. 2015. A randomized trial to assess the potential of different beverages to affect hydration status: Development of a beverage hydration index. American Journal of Clinical Nutrition,103 (3). 717-23.
Medline Plus https://medlineplus.gov/ency/article/002417.htm
NASM (National Academy of Sports Medicine). 2017. McGill, E.A., & Montel, I.N. (editors). NASM Essentials of Personal Fitness Training (5th ed.). Burlington, MA: Jones and Bartlett Learning.
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