Why Am I Salty After a Marathon?

 Have you ever completed a long run and wondered: “what is all that dried crusty white powder covering my face, neck, and running shirt? Am I salty? Why am I salty after a long run?”

Is it my sunscreen dripping? Did I run through ocean air? If this is salt, does that mean that my diet is too salty? Why isn’t my friend covered in dried salt if we ran the same distance?

These are all good questions, and ones that I hear frequently from runners when I provide ART services at the finish line of local races. The short answer to these questions is: Yes, that is salt! The longer answer is still, yes, that is salt. But this phenomenon doesn’t happen to everyone, so here’s the deal about being salty after a marathon:

Nearly everyone loses fluids when they sweat, but some people are saltier sweaters that other. Thanks to the clever scientific properties of osmolarity, we can state in basic terms that sodium and water travel together. When we eat a handful of salty pretzels, our body retains water in an amount appropriate to match that salt increase. (People with chronically low blood pressure often need to add sodium to their diet so that their bodies hold onto more fluid, which prevents a decrease in fluid volume. When there is a larger volume of fluid in the blood vessels, there is a corresponding higher pressure.) When we sweat (either caused by exercise or by sauna), we lose water, and the sodium in our blood stream is drawn out with that water.

It may make sense at first thought, that if you are seeing a lot of salt on your running cap, that maybe your diet is too salty and therefore you shouldn’t eat anything salty after a long run. Quite the opposite is true in most cases however; the salts on your face indicate that you have lost sodium, and thus need to replace it with a salty beverage or food. Remember, sodium and water are travel companions, so if you are running a marathon and only hydrating with water (no salt tabs or sodium containing sports drink or salty snacks at water stops) and you are still sweating, you are still losing salt and water, but you’re only replacing the water! This dilutes the sodium:water ratio, leaving you prone to hyponatremia.

Let’s look at some numbers:

The average RDA sodium is 1,500mg  to 2,300 mg depending on your source (1).

2,300 mg sodium = approx. 1 teaspoon of salt.

The average sweater loses the equivalent of 500mg sodium in one hour of exercise (assuming they lose one pound of sweat per hour)(2).

If you’ve ever tracked what you eat for an entire day, you may have noticed that it’s actually quite difficult to meet the 2,300mg sodium goal on a whole foods based healthy diet. Eating fast food and processed foods daily can get you there quickly, but many nutritious foods don’t naturally contain a lot of salt.

Let’s look at an example. Betty tracks her diet for a week and learns that she naturally consumes about 1,000mg sodium on an average day. She doesn’t eat anything out of the ordinary on the Friday before the Oakland Running Festival so we can assume she has eaten 1,000mg sodium. She runs for four hours on Saturday, which means she’s lost 2,000mg sodium. (4 x 500mg). She takes one salt tab (200mg sodium), some salty peanuts (100mg sodium), and some electrolyte drink (200mg sodium) during the course of the marathon for an additional 500mg sodium). Unfortunately, that leaves sweaty Betty with a sodium deficit of 500mg!

Some people’s sweat will contain more sodium than others, so depending on Betty’s constitution, she may feel just fine at the end of the day, or she could suffer from headaches, nausea, and fatigue (greater than that of an average marathoner).

Should Betty care to rectify the situation, she could intake an additional 500mg sodium. This translates roughly to ¼ tsp of sea salt. The following is an easy to make sports drink that will replace sodium as well as hydrate you during your long run. It’s free of added chemicals and colorings.

*Squeeze one orange into a container with a lid (Or pour in ¼ orange juice).

*Squeeze one lemon into the container.

*Stir in ¼ to ½ tsp. sea salt.

*Fill the container up with cool water to dilute as desired.

A regular sized “Nalgene” bottle seems to hold the proper volume such that the drink doesn’t taste too diluted. Unless you are very sensitive, you won’t even taste the salt! As with any nutritional or medical advice, please check with your primary care doctor to rule out any underlying health issues (such as sodium-sensitive-hypertension) that might contraindicate sodium intake.

(1) American Heart Association (AHA) RDA of sodium: 1500 mg

(1) Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion. Sodium Fact Sheet: http://www.cdc.gov/salt/pdfs/Sodium_Fact_Sheet.pdf: 2,300 mg

(2) http://www.active.com/nutrition/articles/salt-and-athletes-shake-it-or-leave-it

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