What Are Electrolytes?

The truth behind those all-important minerals

We all know to replace electrolytes when riding, and all good sports drinks will contain them. But what, asks Kate Hodgins, exactly are they, and why do we need them?

According to accredited sports dietician Dr Sarah Schenker, electrolytes are salts and minerals present in our body tissues, muscles and blood. In chemical terms, they are ions that conduct electricity in the body.

What makes them so critical is that they regulate thirst and enable your muscles and nerves to function. The balance of these salts and minerals needs to be just right to help our muscles work at their peak, optimising our riding performance, and ensuring our overall health.

What are they?

“Electrolytes are positively and negatively charged salts and minerals that allow messages to be passed from the brain to the muscles,” says Schenker. “Without them, our muscles will cramp, become weak, and lose power.” However, with too high a concentration of electrolytes we feel sick, dizzy and, in extreme circumstances, may end up in a coma, or even dead.

“In the body, electrolytes take the form of sodium, potassium, calcium and bicarbonate,” says Schenker, “but in our sweat we lose more sodium, making it the most important to replace on a ride.”


Usual blood levels for sodium are around 3,300mg per litre. The Institute of Medicine (IOM) recommends that adults should consume 1,500mg of sodium each day to replace the amount lost. For endurance athletes this ﬁgure is higher. How much higher is hard to specify.

“The variation in sweat rate and sweat sodium content between individuals is so large that average values are largely meaningless,” says sports, exercise and health sciences professor Ron Maughan. For example, in an average athlete, the sodium concentration of one litre of sweat can range from 800-3,600mg, but an unﬁt person’s sweat may contain 4,500mg.

What causes the variation?

  • Clothing: Clothing that doesn’t let your skin breathe will cause increased sweating.
  • Salt intake: If you eat more salt, you’ll sweat more salt.
  • Genetics: You may come from a family of heavy sweaters.
  • Athleticism: The sweat of a very athletic person is likely to contain fewer electrolytes.
  • Temperature: Hot environments will up your sweat rate.

Isn’t salt bad?

Salt is 40 percent sodium and the IOM states 5,800mg (one teaspoon and 2,300mg of sodium) is the upper level of salt consumption per day. High salt intake is linked to elevated blood pressure, heart disease and strokes.

However, a 2006 study of marathon runners showed low sodium blood content (under 135mg per litre) caused confusion, vomiting, headaches and seizures. Therefore, moderate amounts of salt and sodium are essential.

Replenish your supplies

“In endurance events, heavy sweating can disturb your electrolyte balance, and you will also become dehydrated,” explains Schenker. “The feeling of thirst is triggered by the electrolyte imbalance.

“Sports drinks with added electrolytes aid the absorption of both the ﬂuid and electrolytes into the blood, hydrating you quickly and getting your muscles back to peak strength.” Look for a sports drink containing between 400 and 1,100mg of sodium per litre.

There are categories of sports drink. These are:

  • Isotonic drinks: The concentration of salt and carbohydrate is similar to in the body, allowing for rapid absorption. They are the usual choice for cyclists while riding because they hydrate and supply muscle fuel and electrolytes.
  • Hypertonic drinks: With a higher concentration of salt and carbohydrate than in the body, they are slightly slower to absorb and are usually used several hours before or after an event. 
  • Hypotonic drinks: The concentration of salt and carbohydrate is lower than in the human body, making them easy to absorb and therefore a popular choice on ride.

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