Why Athletes Need to Think About Salt

If you’re an endurance athlete, chances are you may not need to cut back on salt, like most people should. On average, marathon runners, lose between 17 ounces, to more than 68 ounces (500 milliliters to 2 liters) of fluid every hour from sweating, and in that sweat, they’ll lose between 530 and 2,130 mg of sodium—that’s almost a teaspoon of salt in just one hour! If you’re not replenishing these losses, your performance will suffer—you need sodium to maintain blood pressure, and ensure your muscles and nerves work properly. Signs you’re low on sodium include muscle cramps, fatigue, and headaches. In rare cases, abnormally low sodium levels could lead to hyponatremia, which is serious, and can be fatal.

So what should you do to prevent your sweat from derailing your efforts on race day?

Lauren Antonucci, MS RDN CSSD CDE CDN, and triathlete says, “Because the amount of sweat and sodium athletes lose is highly variable, it’s important to understand individual needs and develop a personalized plan, including both fluid and salt.” Ideally, you should seek advice from a sports dietitian, especially if you have high blood pressure, but to help get you started, Antonucci shares how she develops a sodium strategy for her clients.

Step #1: Perform a Sweat Test

Figuring out your sweat rate—how much sweat you’re losing per hour of exercise—is the first step towards coming up with your personalized plan. Start by weighing yourself (naked), before and after a training session, and factoring in how much fluid you drank or lost in the loo. Knowing that 1 pound of body weight equals 16 ounces of fluid, you can calculate your sweat rate.  

Losing more than 2 percent of your body weight, means you’re dehydrated, and your performance is likely to suffer. If your weight went up, you’re drinking too much fluid, and should drink less. If you’re losing more than 40 ounces per hour, you’re a “heavy sweater,” and will find it tough to drink that much every hour—in this case, Antonucci recommends that you aim to replenish 75 percent of what you’re losing.

Step #2: Determine If You’re a “Salty Sweater”

You can get your sweat professionally tested for sodium levels, but it’s expensive, and simply looking at your skin can be just as good. If you find yourself covered in a layer of salt after a workout, notice white residue on your workout gear, or happen to be prone to muscle cramps, you might be a “salty sweater” and may want to consider adding some sodium to your diet. Your body is also really good at sending you signals—if you’re craving salt after a long run, grab a salty snack.

Step #3: Munch on Salty Snacks

Getting the right sodium balance isn’t as simple as adding more salt into your diet everyday. “Your body will adapt to a high salt diet, and your sweat will become even saltier,” warns Antonucci. “I get my athletes to load up with salt one day before an event, which helps with fluid retention, so they go into a race hydrated too.” Here are some salty snacks to reach for before an endurance event:

•      Mini bag pretzels (1 oz/30 g) – 352 mg
•      10 olives (0.5 oz/15 g) – 420 mg
•      A pinch of salt added to each main meal – 465 mg
•      1 tablespoon soy sauce (15 ml) – 879 mg
•      1 can tomato juice (11.5 fl oz/340 ml) – 978 mg
•      1 cup chicken noodle soup (1 cup/8 oz/240 ml) – 979 mg
•      1 large dill pickle (5 oz/135 g) – 1095 mg

Step #4: Know When to Take Salt Supplements

A few hours into a long event, you may want to think about supplementing with sodium. Antonucci tells her clients to do the taste test: “Put your tongue on the salt, if it tastes fantastic, or even neutral, then most likely your body needs it,” she says. “However, it if tastes metallic and terrible, you probably don’t need it. Wait another hour, and then try again.” This advice holds true for all endurance athletes, because the amount of sodium in your sweat changes depending on your diet and hydration, the weather, and your fitness level—meaning, someone who isn’t normally a “salty sweater” may be on that particular day, so it’s wise to check and avoid the risk of hyponatremia.

Sodium chloride is the primary electrolyte in sweat, with potassium, calcium, and magnesium present in smaller amounts. Many sports supplements contain sodium, but some have more than others, so be sure to check the numbers. Here’s what you are likely find in common sports supplements on the market. (Remember to test any new supplements a few times in training before race day, as salt tablets can sometimes upset a stomach.)

•      Electrolyte spray (10 pumps) – 48 mg
•      Sports gels (1 packet) – ~55 mg (depending on flavor)
•      Endurance Sports Chews (4-5 chews) – 60 mg
•      Packet of salt (0.5 to 0.75 grams) – 190 to 290 mg
•      Oatcake crackers (4 oatcakes) – 280 mg
•      Powder stick (½ packet) – 300 mg
•      Electrolyte tablet (1 tablet) – 360 mg
•      Regular sports drink (32 fluid ounces) – 400 mg
•      Endurance Formula sports drink (32 fluid ounces) – 800 mg

It’s possible to be a light sweater and for it to still be super salty, or to sweat a lot but lose little salt, so Antonucci suggests starting with the averages, and tweaking it to meet your needs. “Endurance Formula sports drinks are served at most Ironman, triathlon and distance running events, so grab a cup every 10 to 15 minutes or so, to take in about 32 ounces of liquid and 800mg of sodium every hour. From there you can adjust the fluid or top up the salt, as needed,” says Antonucci. Before each race, check the race organizer’s website, so you know exactly what will be served. That way you can arrive prepared and ready to focus on getting across that finish line.

Tracy Morris

Tracy Morris is Fitbit’s Lead Nutritionist. With a master’s degree in nutrition and dietetics from South Africa, she’s also an Australian Accredited Practising Dietitian, and an international member of the Academy of Nutrition and Dietetics in the US. Over the past 20 years, Tracy's lived in five different countries, inspiring people around the globe to be healthy. She currently lives in sunny Sydney, Australia where she helps Fitbit fans around the globe live their best lives. When she’s not working, running after her three young kids, or practicing pilates, she can be found sipping pinot noir with her husband watching the sun set.