Monday, August 10, 2015

Sports Drinks Cannot Replace Your Sodium Levels During Exercise


Gatorade- thirst quencher, but can it replace your sodium levels?
Last week I wrote about what causes muscle cramps. I also said I will write about why the Sports drink/ fluid replacement companies are inaccurate in telling us that sports drinks like Gatorade, Powerade and Endurox etc. can replace electrolyte losses.

When you sweat, your electrolyte levels begin to rise! Yes, you read correctly. Let me explain more.

Let's say you have five cups of water and five teaspoons of salt in your system. If you remove one cup of water and a teaspoon of salt, the balance remains the same. There is a teaspoon of salt for every cup of water (i.e. a concentration of 1.0).

Now if you lose 2 cups of water (like when you exercise) and a teaspoon of salt, you've lost more water than salt. The concentration of salt has now risen to 1.25. Your salt (and electrolyte) levels are now higher and will remain higher as you become more dehydrated.

Apply this concept to our physiology. Our sodium (salt) concentration of blood is about 140 mM (or 3.2 grams of salt in every litre of blood). Our sweat has a sodium concentration between 20-50 mM. So even for "salty sweaters" (people who lose more salt than others when they sweat), they lose about 1.1 grams of salt max in every litre of sweat.

Thus, the theory that muscle cramping is caused by low electrolytes as a result of sweating cannot be true. You definitely lose more fluid (or water) than sodium when you sweat.

Sports drinks are incapable of maintaining your body's sodium levels during exercise despite what the manufacturers and advertisers tell you. The sports drink industry has created a perception  that its electrolytes that will help prevent a decrease in sodium.

As explained above, sweating does not decrease your sodium levels, it causes an increase in sodium levels. Sports drinks actually contain insufficient sodium to counteract the effects of sweating on the blood's electrolyte concentration. In fact it causes your sodium levels to fall further.

A sports drink usually contains approximately 18mM of sodium (or 0.4 grams of sodium per litre). That means if you drink a litre of Gatorade (or 100 plus, Powerade etc) during exercise, you can replace a litre of fluid, but only 0.4 grams of sodium.

Blood normally has 1.4 grams of sodium per litre, so even a sports drink replaces more water relative to salt and will only lower your sodium concentration. You CANNOT elevate or even maintain your sodium levels by drinking a sports drink. It is impossible.

Of course if the alternative to sports drink is water, then sports drinks can help prevent sodium levels from falling further.

The key point is that a sports drink will still cause a decline in sodium levels, though less compared to water.

The act of drinking is what causes the reduction. To prevent your sodium levels for dropping further, you're better off not over drinking in the first place.

It's better to listen to your body and obey what it suggests you to do.

Now you know.

References

Science of Sport - Sports drinks, sweat and electrolytes Part 1

Science of Sport Muscle cramps Part IV

Dugas J (2006). Sodium Ingestion And Hyponatraemia: Sports Drinks Do Not Prevent A Fall In Serum Sodium Concentration During Exercise BJSM. 40: 377. DOI: 10.1136/bjsm.2005.022400.


Sports drinks we have in Singapore
If I have to, I prefer Pocari- "tastiest" to me

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