In defense of salt (why you need more than just water on a long run)

I’ve been getting A LOT of questions lately about sodium and hyponatremia, so I wrote something up on the subject:

Hyponatremia, a drop in sodium levels, can occur due to the loss of sodium and chloride during extreme sweating (sodium, chloride, and water are the major components of sweat). Usually, when you sweat, you also lose plasma volume due to the loss of water, but some people consume a lot of water without salt. This causes the plasma plasma osmolarity (basically, ratio of solutes to fluid in the plasma) to increase even further. When plasma osmolarity decreases it will actually cause more water to be excreted by the kidneys (meaning you are peeing it out) in an attempt to maintain plasma osmolarity. The problem is that this signals your brain that you are thirsty, meaning you will continue to take in water despite the fact that you don’t actually need it. And you kidneys can only excrete so much at one time.

So what? Well, when plasma osmolarity is too low, it can cause your cells to swell to the point of bursting. Your brain can swell, causing the CNS symptoms seen in hyponatremia. I’m sure you all know brain swelling is bad, but you may not realize that it can cause a coma and even death. Furthermore, sodium is an essential ion for things like muscle contraction.  Basically, you can’t just replace sweat with water for a long period of time.  Your body can’t make it’s own sodium, so it needs salt.  Salt can be found in sports drinks, gels, and salt pills.  Or in a salt shaker.

Questions? I TA’ed Human Physiology for two years before going for my PhD in the subject, so I’m happy to try to answer any random phys question you might have for me (and yes, I do know what makes it light vs dark meat, you wouldn’t believe how often I’ve gotten that question).

Sorry for the short post, but I’m exhausted and need to go to bed early.  And I want to finish my incredibly strange book (Bumped by Megan McCafferty).  Also, Rufus ate half a cardboard box, so I suspect we have some serious poop coming on.  Tomorrow I will post my 7 links if I survive my 7 mile run in the blazin’ heat.  Good thing there is a new FroYo place opening up down the street tomorrow!  50% for grand opening means I am there!

Any exciting weekend plans?  Seriously, hit me with your phys questions, I’m a giant nerd, so I love researching them.

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About Sarah S @RunningOnWords

Married 20-something in flux and trying to cope by running and occasionally crafting.
This entry was posted in Dogs, Medical, Science, Training. Bookmark the permalink.

13 Responses to In defense of salt (why you need more than just water on a long run)

  1. Kim (Book Worm Runs) says:

    Thanks for the info!! Some scary stuff!! So, I have heard people take salt tablets…but for my level of activity I am sure the gels and the Gatorade are just fine, right? It isn’t like I am an Ironman or something 🙂

    Good luck on the run tomorrow…I have 10 miles scheduled and I am starting WAY early to avoid the bad heat!

  2. Pahla says:

    Ummm, well now I’m curious about the light and dark meat thing.

  3. Abby says:

    Second-and experience with hyponatremia, watching Brent get sick in Costa Rica. It’s a scary thing.

  4. What is FroYo and where is it going to be because I think I need to try it!

    Great post….helpful!!!

  5. I started using SaltStick tablets because when i moved to florida I was in fact flushing my body of electrolytes with all the water I was drinking and nearly dropping like a fly on my runs.

  6. emily says:

    Good info. I’m scared of “overheating” outside while running. I love running when it’s hot, but not in this humidity. I’ve begun drinking Gatorade after my workouts. I wonder if that’s helping me.

    Also, frozen yogurt is my favorite! We have to drive a good 45 minutes to get to a frozen yogurt place, but you better believe we’ve made the drive..just for the froyo 🙂

  7. elohorn says:

    I am so impressed by how knowledgable you are!!! It always puts me in absolute awe when people are good at science/math b/c that’s sooo not how my brain works.

    I DO have a question about potassium… I took a biomedical ethics course last year & the professor said something about Terri Schiavo, that if she would have eaten a single banana then her coma could have been prevented, and I always wondered if that was an exaggeration. How crucial is potassium?

    Anyways, sorry for the super long comment, but I love Megan McCafferty too! Her sloppy seconds series was a great read 🙂

  8. Mandy says:

    Great post!!! Often – for endurance athletes, lack of salt is the biggest risk. I thought I read somewhere that more marathoners die from not replacing their salt than from dehydration. It definitely can hurt you quickly.

  9. Great post! Thanks for sharing your knowledge. 🙂

  10. That’s why I like Gatorade a little more than coconut water for hydration if I’m going to be sweating so much – the sodium!

  11. Kara says:

    A frozen yogurt place? I’m jealous!

    Yes, that was my main takeaway here, but frozen yogurt is a big deal!

  12. Sara W. says:

    Oh my gosh! Thank you for clearing up the salt issue for me. I knew we needed salt on long runs (which is why the Gatorade), but I never understood why. Now I do – makes perfect sense! Do the salt pills give you more salt than a sports drink?

    I love asking medical/body questions – thanks for your insights! 🙂

  13. Pingback: A Giveaway from Someone Else « Where Do We Go From Here?

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