Six Things You Always Wanted to Know About Electrolytes (But Were Too Afraid to Ask)

Getting the right amount of electrolytes is key to peak athletic performance, avoiding cramps, and preventing dehydration. Here's everything you need to know.

Molly Hurford |

The information revolving around electrolytes is almost more superstition than science: we know that they exist and we know we need them, but many don’t really know what they are or why we’re always adding them to our drinks. To sort the myths from the facts, we’ve asked Lindsay Baker, a principal scientist at the Gatorade Sports Science Institute in the US, to demystify electrolytes, and explain why they really do matter.

What are Electrolytes?

Electrolytes are, at their most basic, minerals found in your blood, sweat and urine. The ones you’ll hear about most often are sodium, magnesium and potassium. Among other things, they affect your fluid balance.

Why Do They Matter?

“Sodium in particular is the main electrolyte in your plasma, and helps draw water into that space,” says Baker. It also plays a role in transferring electrical currents between nerves and cells. The right fluid balance affects everything from neurologic function to muscle contractions—which is why you might find yourself irritable and cramping when it’s off.

“Athletes also sweat, and sodium is the primary electrolyte lost in sweat,” says Baker. Because of sodium’s role in water retention, this can create problems. “When you have enough sodium, your kidneys can do a better job of retaining the fluid that you need.” says Baker. But when you fail to replace that sodium, you’ll lose more fluid when you pee, leaving you more dehydrated, even if you’re drinking water.

Which Electrolyte Is Most Important?

Magnesium and potassium are often discussed, and they are important, Baker says, but the one you really, truly need during a hard workout is sodium—especially during efforts that are long (endurance) or hard (intensity). You’ll find the other electrolytes in most sports drinks, just in smaller concentrations, because you don’t lose magnesium and potassium at the same rate as sodium.

How Many Different Kinds Do I Need?

If you’re a serious athlete looking for perfectly dialed nutrition, consider a sweat-rate test, which looks at how much sodium you’re losing in your sweat. Some people sweat more than others, and even people who don’t seem to sweat much can still lose higher levels of sodium than those who sweat buckets.

If you’re less committed but still find yourself cramping or getting grumpy during hard efforts, try adding some salt to your sports drink—Baker says a good general rule is to aim for between half a gram to a full gram of sodium per liter of fluid.

Does It Matter How I Take Them In?

While most recommendations for sodium are in beverage form, you can get it from other sources, as long as you’re getting the right amount. What you want to remember, Baker says, is that you need both water and a bit of sugar to help the body actually absorb the electrolytes (and, of course, to rehydrate!). So you can also get your sodium from gels and bars, but “make sure you drink enough water to help with digestion and absorption,” Baker warns.

What About When It’s Hot?

Temperature definitely matters, Baker says. Because sweating can help cool us, you’ll need more electrolytes on hot days.

Read: Is Your Water Hydrating You?

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