The importance of staying salty...

by ericgu 18. August 2007 04:59

Salt (or at least the sodium component of it) is perhaps the most underappreciated and under-discussed nutrient for endurance cyclists.

Given my recent history, I've been doing a fair bit of research into the topic, and frankly I've been surprised how little information there is. That, coupled with a lot of bad press around sodium because of its well-established link to hypertension, means that most cyclists don't think about salt. They do perhaps think a bit about hyponatremia.

Which is really a bit strange, when you think about it, as many of us have white stains on our helmet straps and that sandy feeling on our faces after a hard ride.

So, here's what's going on WRT salt, and a few things that you might want to think about.

When you sweat, you lose salt, along with a number of other electolytes.

Here's a table I pulled from Burke's Serious Cycling

  Sodium
(mEq/L)
Chloride
(mEQ/L)
Potassium
(mEq/L)
Magnesium
(mEq/L)
Blood Plasma 140 100 4 1.5
Muscle Tissue 9 5 160 30
Sweat 40-60 30-50 4-5 1.5-5

This chart uses mEq/L, which is basically a measure of the concentration of the various elements. What we'd like instead is a chart that shows the actual amount of the substance (which we get by multiplying by the molecular weight). My wife tells me that medicine is the only place that uses mEq/L as a measure...

Here's the converted chart:

  Sodium
(mg/L)
Chloride
(mg/L)
Potassium
(mg/L)
Magnesium
(mg/L)
Blood Plasma 3220 3550 156 18
Muscle Tissue 207 172 6240 365
Sweat 920-1380 1065-1775 156-195 18-122

This chart shows the difference between salt (sodium and chloride), and the other major constituents of sweat. For potassium and magnesium, the concentration in the blood is fairly low compared to the concentration in muscle tissue. This means that loses of those two elements through sweat are relatively unimportant to the body's total supply.

For sodium and chloride, however, the amount stored in muscle tissue is fairly minor. The majority of the storage is in the blood. And there's really not that much there.

So, say that you're out riding and only taking in water. Your sodium level drops. Your body wants to get rid of the water, but it doesn't want to lose more sodium, so it stashes the water between cells, and you're on your way to hyponeatremia.

This happens more quickly if you're on a low-salt diet, which is what got me into this topic in the first place.

What that means is that you need to replace the salt. Serious Cycling suggests that you need from 400-1100mg of sodium and 500-1500mg of chloride. ACSM recommends 500-700mg of salt/liter.

Many hydration drinks have some salt in them - here's a good comparison chart. Searching through that chart, I find that the accelerade that I drink only has about 500 mg of sodium per liter. That's at most around 50% of the amount I need to replace the salt I sweat out (I'm a fairly salty sweater). Which explains a lot.

Almost all of the the drinks have some electrolytes - as they're needed to help you absorb the drink - but some of them are pretty low. So, take a look at what your drink has in it, and that will help you figure out if you need supplementation. If you are riding for long periods, my guess is probably *yes*.

Symptoms:

  • Fatigue (yeah, I know, it's a bit hard to judge after 60 miles)
  • Upset stomach
  • Headache
  • Aversion to sugary foods (I get this rather than a salt craving, though salt tastes good. This may also just be food fatigue)
  • Weight gain during the ride
  • Lack of urination, especially if you are drinking a lot.

A note on hypertension...

If you have hypertension (high blood pressure), this is an area that you will want to be careful with, and you may want to consult your physician before supplementation.

What supplements to use

A classic supplement is beef jerky, which tends to be around 1000mg per service. If you want a capsule you can swallow, both Lava Salts and Succeed E!Caps have a good reputation on the ultra (bike/run) sites.

A lot of people talk about Hammer's Endurolytes capsules. The hammer hydration products are quite low in electrolytes (see the chart I linked to earlier), and frankly, I'm mystified by what's in the endurolytes - they only have 40mg sodium and 60mg chloride, which is a really small amount. They suggest that you can take up to 6 of them per hour, but even that may not be enough. They do have other electrolytes, but you are probably okay without supplementation of potassium and magnesium during exercise.

One final note

As with all things related to nutrition/hydration, people have different responses, so you'll probably have to play around to find out what works for you. If you are used to sweating a lot, your body has likely adapted so that you don't lose as much electrolyte when you exercise. Conversely, if you don't work out in the heat and/or don't sweat as much, you may be near the upper end of electrolyte loss.

References

Ultracycling has two great references on this:

Low Blood Sodium

Water and Salt Intake during exercise

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