The Truth About Dehydration

Posted on Posted in blog, science

Why do we, as athletes, feel the need to obsess about what to drink or how much to drink for racing and training? When did we switch from making that decision for ourselves to letting others dictate how much we need to drink while exercising? Can you think of any animal in the world that is told by another animal/person/book when it should drink? As the saying goes “You can lead a horse to water but you can’t make it drink”. Perhaps that is because the horse knows he isn’t thirsty.

Who is telling us when and how much to drink? Why do we listen to them? Is it out of fear that our performance will suffer? Perhaps we fear that there are potential health risks? What health risk are we fearful of; dehydration, heat stroke, cramping?  Do other animals have these fears or suffer from these health issues while playing in the sun?

It is important that people are asking questions about dehydration. However, what people don’t realize is the danger is not dehydration but rather over hydration and hyponatrimia (and the result of hyponatremia can be death!). I don’t know about you but death is certainly not on my to do list.  There has never been a reported death during an endurance event due to dehydration but there have been multiple deaths due to exercise-induced hyponatrima. I know you are itching to know what hyponatrima is and how to avoid death and I will get to that! However, first we need to understand why we should not fear dehydration and I promise it will help you avoid hyponatrima.

Why is dehydration not a danger? Everyone from your mother to your doctor tells you to drink a lot so you  don’t become dehydrated. I too have been told this from day one of football practice as a 4th grader. So my question to them is: what will happen if I do become dehydrated? The answer to that (as defined in medical terms) is: you will become thirsty! Thats it?!? Yup, dehydration is just the reduction of total-body water content and once that causes the sodium concentration to rise (osmolality) the brain detects the change and develops the symptom of thirst. Yup, that basic.  There are no other symptoms associated with dehydration; thirst is the only symptom.

When fluid is lost from the body through things like sweat and urine the concentration of sodium in the blood actually rises which causes the brain to send the message for secretion of AVP/ADH (hormones) which tells the kidney to reabsorb some water. The brain also triggers the cingulate gyrus which increases your thirst.  So by reabsorbing some water from the kidney and sending the thirst signal (telling you to drink) the blood regains its normal blood osmolality (sodium levels). So if you are actually thirsty you are drinking because the water level of your blood is low which increases sodium concentration. You have to add water back to the blood to lower the sodium concentration.

Do people die from dehydration? If the thirst cannot be quenched because fluid is unavailable (i.e. stranded in a desert) then the body activates a bunch of emergency plans but ultimately major body organs will fail which will most likely lead to cardiovascular collapse. So YES, you can die from dehydration if you are stranded for days without any access to water. Personally, I have never been in a race/event situation where the race director restricted water availability.

Based on the information above I personally don’t see dehydration as something to fear while exercising or racing in any situation. If you get thirsty, drink.

Sport Drink companies have led us to believe that dehydration is both dangerous and will negatively affect our performance.We have now addressed the issue of danger and in a later blog post I will discuss performance. A little spoiler —  they are misleading you on that point as well.

The next part of this series will talk about what we should actually fear, which is Exercise-Associated Hyponatremic Encephalopathy (EAHE), or water intoxication, which can lead to death.


Bottom Line:

The sport drink industry has created this fear of dehydration so that people feel compelled to buy their product. It is consumer marketing at its best.

That fear is unwarranted when we have free access to water because of our bodies natural ability to control blood sodium levels with the simple symptom of thirst. It is also important to note that you must NOT ignore the symptom of thirst or you risk triggering the emergency plans to conserve water and begin damaging organs. So don’t drink on a schedule, just listen to your body and drink when you are thirsty.



Work, Live, Tri

Coach Hammond

Leave a Reply