Water temp to maximize hydration speed?

December 26, 2006 8:02 PM

What temperature water will hydrate one fastest?

Is it hot, cold, or somewhere in between? (And why?)

My friend says hot water is best. In which case, is cold water "refreshing" only because of its thermoregulatory properties, not because of how fast it quenches one's thirst?

posted by Humpable Prose to Science & Nature (12 answers total)

I have no science to back this up, but I always drink my water at room temperature because too hot or too cold prevents me from using my preferred method which is drink half the bottle in a single pull.

So as a sample size of one, I personally get hydrated most quickly by having the water neither too hot or too cold, but just right.
posted by quin at 8:17 PM on December 26, 2006

Comparison of Efficacy of Oral Rehydration Fluids Administered at 37°C or 23°C

"There were no differences between the groups with respect to weight gain, rapidity of rehydration, frequency of vomiting, or overall efficacy. Nor were there differences between infants rehydrated using the rotating 2:1 (GES:water) or bolus 2:1 oral rehydration methods. Oral rehydration fluids can be administered at ambient temperatures and need not be warmed to 37°C."
posted by stavrogin at 8:32 PM on December 26, 2006

In the most common conditions where a healthy person might seek rehydration-- you are hot and sweaty from exercise, or it's a really hot day and you're thirsty-- I think cold water will rehydrate fastest, because the cold water will quickly lower body temperature, which will reduce sweating, evaporation from sweating, and evaporation from your lungs and the mucus membranes of your breathing passages, all of which are sources of water loss which would continue at higher rates if you drank hot water instead.
posted by jamjam at 9:13 PM on December 26, 2006

Water in your stomach will rapidly come to ambient temperature -- i.e. ambient inside your body. The temperature it was when you drank it will only matter for a minute or two. After that, it's all the same temperature.
posted by Steven C. Den Beste at 9:21 PM on December 26, 2006

Room temperature is best. Too cold and your body does too much work to warm it up, and so it goes through you. Too warm, and it has to cool down inside of you.

You shouldn't drink a lot of water all at once, as it doesn't hydrate you as well. Instead, you should take it in all day.
posted by Camel of Space at 9:31 PM on December 26, 2006

My biology teacher once told me iced water can lower core temperature and so convince your body it's cold (despite you being hot peripherally due to muscle activity). It'll then step up sweating, etc.

But I can't find a ref on a (rather cursory) Google search, so maybe not true.
posted by TrashyRambo at 9:44 PM on December 26, 2006

Camel of Space : You shouldn't drink a lot of water all at once, as it doesn't hydrate you as well. Instead, you should take it in all day.

Bah, despite the eponysterical-ness of your comment, you clearly have never suffered the harsh recriminations of a badly spent night-out-on-the-town. Sure it might be "better for you" to slowly take in water, but when you are desperately hung over with no hope for parole, chugging water is the fast track to less pain.

Just sayin'
posted by quin at 10:04 PM on December 26, 2006

Actually you should not be concerned with the temperature but with the frequency of re-hydration.

As a young adult I worked several jobs where I was kept out in the heat too long. Some times it almost seemed that I had gotten so dehydrated that I was no longer able to sweat. Afterwards when I could guzzle water I shortly broke out in a freaky body covering layer of sweat.

The temperature of water has nothing to do with "rehydtation". However if somebody is so dehydrated that their core body temperature has risen then they would appreciate some cold water to lower this temperature.

I wish you luck with applying these lessons from people who have really sweated to your (maybe personal trainer) lifestyle.
posted by MonkeySaltedNuts at 10:05 PM on December 26, 2006

Monkey is closest to what I've come across in writings about hydration and cycling. The study that I came across said that (for some reason), people drank cold water less frequently, but not because it was a shock to the system. It wasn't the temperature per se that affected hydration rates or anything, it was just that the lower the temperature the less frequently people felt like drinking.
posted by rhizome at 12:00 AM on December 27, 2006

Room temperature is best. Too cold and your body does too much work to warm it up, and so it goes through you. Too warm, and it has to cool down inside of you.

I've always had a question about this. Wont your body warm it to body temperature anyways? So by that argument shouldnt you be drinking 98 degree water?
posted by vacapinta at 11:09 AM on December 27, 2006

On a completely non-scientific basis, I'd argue that cold water rehydrates people better simply because warm water tastes horrible.

As such, they drink more of it.
posted by mr_silver at 1:09 PM on December 27, 2006

On a completely non-scientific basis, I'd argue that cold water rehydrates people better simply because warm water tastes horrible.

I second this: I cannot get over the impression that plain hot water (not a vehicle for coffee, tea, lemon juice and sugar, etc.) tastes like bath water. Exercising in very hot weather, you take your water bottle along, and the water heats up to ambient temperature. Disgusting.
posted by bad grammar at 6:59 PM on December 27, 2006