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+.
Most runners know they need to replace electrolytes lost in sweat—that’s the whole idea behind carrying sports drinks on long runs. But did you know that your daily diet is filled with a wide range of them from whole foods that enable many important functions in your body?
Sodium is the most famous of the bunch, both for its reputation as a major constituent of sweat, as well as for its excessive presence in the American diet. But optimal fluid and electrolyte balance beyond the salty stuff is essential not only for good health, but for athletic performance.
What are Electrolytes?
Electrolytes are intertwined with all fluid in our body—not just sweat. Minerals consumed from foods in our everyday diet dissolve in this fluid, breaking down into small electrically charged (positive or negative), powerful particles. These newly formed charged electrolytes are present in our blood, lymph system, and urine as well as in the fluid between and within our cells.
While they don’t contain energy, they do activate electrical impulses. Muscle contraction requires the presence of adequate sodium, potassium, and calcium; and muscle weakness and cramping can result when these electrolytes are not available in sufficient quantities. Low electrolytes can also cause mental confusion and brain drain. Electrolytes help nutrients move into cells and help water move out to stabilize your body’s acid-base balance. They also affect your heart’s rhythm.
The electrolytes in our body–all of which are important for runners–include sodium, chloride, potassium, magnesium, phosphate, bicarbonate, and calcium. Each one plays an important role. Let’s take a look at each.
As runners, you might already be familiar with terms related to sodium imbalance–hypernatremia (too much sodium) and hyponatremia (not enough sodium). Sodium is critical because, like we mentioned above, it helps to maintain fluid balance, but also helps you actually absorb nutrients. If you don’t have enough sodium it will be hard for your body to properly rehydrate and refuel.
After sodium, chloride is the most abundant electrolyte, though you may not hear about it quite as often. Like sodium, its main job is to maintain fluid balance. Chloride also plays a role in maintaining balance in the body’s pH, which means that if it becomes out of balance you can experience acidity or alkalinity.
Though they are small in size, electrolytes perform many essential functions, often working as a team. As such, potassium works in tandem with sodium. Having a balanced level of potassium is important for heart function. Without enough potassium you’re likely to have muscle cramps or dizziness.
Magnesium’s main role is to turn nutrients into energy. So like sodium, your fuel will be of much less use to your body if you’re low on magnesium.
The main job of phosphate is to help the cells in the body metabolize the nutrients that we eat.
Another less spoken about electrolyte, bicarbonate is made up of recycled carbon dioxide that is not used in normal respiration. Like chloride, this helps to keep your body’s pH in balance.
As kids we are heavily educated on the importance of calcium to build strong bones, but the mineral does more than that. Calcium is actually crucial for controlling your muscles and managing heart rhythm. Having too much calcium can affect many of your body systems including your kidneys (kidney stones, for example), skeletal system (join pain), digestive system, and even cause headaches. Not having enough calcium can cause muscle spasms and, of course, weak bones.
What happens when you sweat?
Electrolyte balance is very carefully regulated by our bodies. When we eat a well-balanced diet with plenty of variety, our kidneys are equipped to keep or eliminate electrolytes as needed. But here is the catch—when you add exercise to the equation, you can lose significant amounts of them in your sweat. Sodium and chloride are the most abundant, and daily profuse sweating can result in substantial loss of these minerals, which will require supplementation. We also sweat lower amounts of potassium, calcium, and magnesium, though it is best to ensure that you target good food sources of these three electrolytes daily.
How can you replace lost electrolytes?
By fueling, of course! During exercise, you can add an electrolyte mix to your water, or consume a sports drink for both the electrolytes and performance-enhancing carbohydrate fuel. Studies show that sodium-containing fluids (or snacks consumed with water) better restore hydration levels than plain H2O. Depending on your sweat rate, you may need to consume anywhere between 300mg to 1,000mg per hour. Sports drinks vary in sodium content, but reach for those with higher sodium levels if you are a salty sweater or when the weather is hot and humid.
When preparing for an event, check your sweat rate by weighing yourself before and after a run so that you can develop
a personalized fluid-replacement plan. Every pound of weight lost during a run reflects 15 ounces of sweat. For each pound, consume 20 to 24 ounces of fluid over the next two hours.
After a long, hard run that leaves you with some level of dehydration, add sodium to your recovery snack or meal. Many protein powders contain sodium (if you’re going the post-workout shake route), and other salty good ideas include tomato juice, crackers, cereals, and breads.