On Sun, 18 Mar 2007 21:55:12 +0100, Mxsmanic
wrote:



Thirst is a reliable indicator of dehydration.

Yes.

An absence
of thirst is a reliable indicator of proper hydration.

No.


While it appears to be true that by the time you experience thirst you are
dehydrated, there appears to be some physiologic lag time after other
dehydration symptoms have occurred but before thirst kicks in.

Only in extraordinarily acute dehydration, which is not a type of dehydration
that occurs when flying an aircraft.

Check out the three articles below. The third one is more technical
and explains the delay between dehydration and thirst.

From personal experience: I used to live in humid areas (Europe and
East Coast of the US) and never felt any simptomps of dehydration
there besides thirst. Now I spend most of my time in the West and
Southwest US and sometimes have a particular headache that goes away
immediately after drinking some fluids. This is more likely to happen
when the air is dry and especially if I'm at higher elevation, e.g.
while flying. I do not experience thirst, the headache is my first
indicator of dehydration.

More knowledgeable people wrote this:
http://sportsmedicine.about.com/cs/h...n/a/022504.htm
http://www.detrick.army.mil/tenants/ih/ehhot.cfm
http://www.water.org.uk/home/water-f...ts/dehydration

- Tom