The weird thing you should be eating during your endurance workout

I'd gone on big hikes before, even touring in the Italian and French Alps around Mont Blanc one year, but nothing prepared me for this. With around 60 pounds on my back, my friend and I embarked on this trip knowing it'd be a challenge.

Soon enough, we were panting our way up to altitudes that made us dizzy, trekking 10-plus miles a day, filtering stream water into our CamelBacks, and—per fellow trekkers' recommendations—taking salt pills and eating salty licorice candies to keep us hydrated. Hydrated, you ask? Yes, indeed.

"Essentially, if you think about yourself, your body is just a big bag of salty water," says John Higgins, M.D., sports cardiologist with McGovern Medical School at The University of Texas Health Science Center at Houston. "Your ability to function is tied in fairly closely with that balance with respect to the salt and the water."

Salt, or sodium, is an electrolyte—one of many, including magnesium, potassium, and calcium—that can be used as a way to replenish your body's depleted supply during intense exercise. What's great about salt specifically is it's easy to carry and take, in pill form or candies, during an endurance, or 90-plus minute, workout.

But why exactly are electrolytes important? Chris Davis, M.D., and Fellowship Director for Wilderness Medicine at the University of Colorado School of Medicine, explains that as we drink water and it goes to our stomachs, it gets absorbed into the intestines. But in order to actually get hydrated, we need those electrolytes to absorb, retain, and distribute the water throughout our cells.

Sweating and body temperature are obviously both factors here, too. "Be mindful that when you sweat, you're not just losing fluids, but you're losing salt," Davis says.

So, the hotter you are, the more you sweat to balance your body temperature, and the more salt your body loses in your sweat. This can especially be an issue in dry climates (as it was for me in Colorado), when your sweat evaporates almost immediately, says Nikolas Harbord, M.D., Assistant Professor of Medicine and Nephrology at the Icahn School of Medicine at Mount Sinai.

"You may not realize how much water you're losing in these drier temperatures," Harbord says. "So you have to be especially aware of your hydration in those climates."

Higgins agrees, saying that if you're sweating more than usual, it could deplete your sodium supply and affect your performance, either in terms of light headedness, a slower pace during a run, or muscle cramps.

As a result, many athletes turn to products like Gatorade (one bottle has 270 mg of sodium), salted candies, and salt pills to keep their hydration levels consistent. Some even resort to oral rehydration solution or therapy—a mixture of one liter of water, half a teaspoon of salt, and six teaspoons of sugar (you can buy a version of it at REI), Davis says.

The problem? There's no one formula that fits for everyone. Of course, every body is different and therefore needs different amounts of water and salt to ward off dehydration. However, there are some ways to keep yourself replenished throughout a workout. First, Davis warns against overdoing it by pre-loading with salt before exercise, since many Americans eat too much salt anyway. (In fact, 90 percent of Americans have too much sodium, according to the Centers for Disease Control and Prevention.)

Higgins—who runs marathons himself and takes SaltStick Caps an hour into his runs, and every 30 minutes after that—says that keeping up that salt intake throughout an intense workout can help your performance. But replenishing after you exercise is important, too. "You're still going to be producing sweat and cooling down after," Higgins says. "So it's important to keep drinking fluids after you exercise as well."

Salt is important for intense workouts or endurance athletes, but if you aren't drinking enough water in the first place, the salt won't be able to do its job. Higgins recommends drinking 16 ounces of water before your workout and sipping a few ounces every 15 minutes throughout. The salt can come in handy here, too, essentially by making you thirstier so you drink more water.

But be careful about how much salt you take in, as the body will only absorb what it needs, sending the rest to your bowels where, if you have too much, it could turn to diarrhea. Salt pills or tablets with around 200 milligrams of salt are a safe bet, Higgins says (his favorites are 215 milligrams).

That's why Higgins especially stresses not to have salt before a typical, moderate workout of 30 minutes or so, as it could lead to stomach troubles. Davis says it can be like dropping a salt bomb on your gut.

The bottom line: Use salty candies or salt tablets for intense, endurance workouts, which is when you really need it. Any more than that and it could be like rubbing salt in the wound.