The Truth About Dehydration- Part II Hyponatrima

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In the last post (The Truth About Dehydration) we talked about the unwarranted fear of dehydration as a health risk to us while participating in endurance sports. I also introduced you to the idea of Exercise-Associated Hyponatremic Encephalopathy (EAHE); which I mentioned should be feared because it can be fatal.


So what is EAHE? Why hasn’t anyone warned you about it? How do we avoid it? All great questions and to answer them we will need to take a look at how we balance electrolytes and water within our body; in particular how water travels into and out of our cells.


Water is generally thought of as a pretty safe thing to drink, I mean it certainly isn’t poison right……or is it? Of course we all know that water is not poison BUT it can become poisonous if we consume to much of it. Water Intoxication (water poisoning) is a potentially fatal disturbance in your brain function that occurs when the balance of electrolytes is pushed outside of the safe limits from over consumption of water.

The human body has many different types of electrolytes (sodium, potassium, calcium, magnesium, hydrogen blah, blah blah blah blah) but sodium is the main electrolyte found in the extracellular fluid which consists of blood plasma and other fluids that are found around the outside of cells. When sodium concentration levels become too low within the extracellular fluid the body restores the correct concentration by removing water. It is basic idea of addition through subtraction: there is not enough sodium in the water so we remove water to increase the sodium concentration.


To regain the balance of sodium to water in the extracellular fluid the body will move water from the extracellular fluid (outside of the cell) to the intracellular fluid (inside the cell). The result of the water going into the cell will cause the cell to swell; similar to adding more water to a water ballon. So what is the big deal if the cell gets larger? Well it is not a big deal if the cells in your fingers or feet start to swell because the skin around the cells will expand to accommodate them. Where it does become a big deal is when the cells in say……your brain start to swell. This becomes a problem because your brain lives inside of your skull and if the brain starts to swell it will get compressed because unlike the skin of the fingers the bones of skull can not expand to accommodate the enlarged cells: this as you can image can cause a major problem.


When the brain cells start to swell due to low sodium concentration it is referred to as Hyponatremic Encephalopathy; if this occurs during or post prolonged exercise it is considered Exercise-Associated Hyponatremic Encephalopathy (EAHE). The swelling of the brain can lead to brain stem compression and respiratory arrest, which in most severe cases results in death.


When we where talking about dehydration remember I said that the only symptom was thirst and that it was a sign to let us know that the sodium concentration level in the serum (extracellular fluid) was to HIGH so the brain told us to drink water to lower the concentration level back to normal. So as we become dehydrated we are actually putting our body in a state of Hypernatremia (sodium level above normal) where the condition of EAHE is caused by the complete opposite situation of the sodium level being to low or Hyponatremia. Now do you see how the fear of dehydration can cause EAHE? If we listen to the fear of dehydration then we just keep drinking and drinking even though we are not thirsty which raises the water level of our body which dilutes our sodium level (lowers the concentration) which puts us in a state of hyponatremia which can cause the brain to swell which can cause hyponatremic encephalopathy which can cause death.


So now that we see that low sodium levels can be a really problem resulting from overhydration there are people and companies out there that would like to sell you sodium pills and products. This my friends is NOT the answer; the simple answer to the problem is to not overhydrate by simply drinking to thirst. Those sport products that tout their level of electrolytes are full of s**t because the sodium concentration found inside of our body is way more concentrated than what we could drink. You would have to try and drink ocean water to come even close the the concentration level and that still would not be enough. Anything you drink, and I mean anything you drink will dilute the sodium concentration. So a big huge: NO! Is the answer to the idea that sodium supplements are a solution to EAHE; the only solution is to simply not overhydrate in the first place.


Bottom Line:

Dehydration is not to be feared in fact fluid loss during endurance events is normal, if not optimal. Studies of top performers in endurance events typically demonstrate weight losses ranging from 2% to 8% or higher; those who win the race are generally the most dehydrated. There has never been a reported case of death due to dehydration during an endurance event where on the other hand there have been 10 reported deaths due to EAHE since 1991. So I ask you: which do you fear dehydration or overhydration?


Side Note:

A healthy individual should not have to fear EAHE because the human body is amazing at regulating these balances and will usually get ride of excess water through urine. BUT if you have a condition called Syndrome of Inappropriate ADH (SIADH) then you do have to worry because you may not feel the urge to pee. This is not something a doctor checks for until an issue arises and is more common than you would think. A study found that as high as 13% of Boston Marathon runners in 2002 could suffer from SIADH. Do you suffer from SIADH…maybe, maybe not….but if you drink to thirst you really don’t have to worry about it.



Work, Live, Tri


Coach Hammond



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