PG and VG are Humectants.
Humectants are additives that bind water and help to retain moisture. Although humectants have applications in many industries - pharmaceutical, cosmetic, veterinary - they are commonly used in foods. Water activity reduction achieved by adding humectants to food enhances stability, maintains texture, and reduces microbial activity.
Humectant use in foods is widespread and has a long history. Salt and sugar are the oldest, most widely used humectants. Other commonly used humectants include sorbitol, glycerol, and propylene glycol.
PG and VG absorb some water when vaped, but the main vapour is produced from the liquid, not from the tiny amount of moisture absorbed from your body. If you attach an ecig to a suction pump, similar to that used in trials for the
Clearstream Protocol, vapour is produced without any contact with the body or other moisture-holding materials.
So yes, vaping will dehydrate you to some extent, proportional to the amount you vape.
John
No chemistry books were harmed in the making of this post ;-)
Edit: Glycerol was formerly classified as a diuretic, but it is now accepted that there is little extra urine flow at doses between 1.0 to 1.5 g/kg. In September 1997, the US Olympic Committee removed the ban on glycerol.