How much, when, and at what temperature should you drink water?

Nowadays it seems like practically everybody is walking around with a water bottle of one type or another. Do we really need to have water with us everywhere we go? I often hear that I should drink about 8 glasses of water per day. A typical glass of water is 8 oz, so that means I should be drinking 64 oz of water each day. That’s a lot of water! Then there is the question of when I should drink all this water during the day, as well as the question of whether cold or warm water is better. There is are even rumors out there that cold water causes cancer. In this post I'll try try to answer these questions and get to the bottom of all this.

First, most of the material I could find about water consumption agrees that if you rarely feel thirsty and produce 1.5 liters or more of colorless or slightly yellow urine per day, your fluid intake is probably adequate. So the answer to the question of how much is to measure your urine volume and make sure that the color is right.
Next, when should I drink the water? Can I drink 4 cups when I wake up and 4 cups when I go to bed (don’t worry, I have a water-resistant mattress pad)? It seems that many agree that the best time to drink water is between meals: drink about a half hour to an hour before and an hour after your meals, and otherwise evenly space your drinking throughout the day. Drinking during meals dilutes your stomach acids and makes digestion less effective. Drinking before and after meals allows your body time to process the water, and it allows your stomach to recover from the dilution.

The cold versus warm issue is more convoluted. Some people believe that drinking hot water can purify the body. The logic behind this is that as you drink hot water your body tries to lower its temperature and this causes perspiration, flushing toxins from your system. The recommendation is to slowly drink one cup of hot water 2-3 times per week. Make sure to avoid drinking hot water from the tap as this is likely to have more heavy metals in it than water warmed external to your water delivery system. Also, if all 8 of your 8 oz glasses of water are cold then you can lose about 70 calories per day from water consumption alone. To put this in perspective, this is equivalent to about 1 tbsp of blue cheese dressing or 1 slice of whole wheat bread. Obviously, if you are exercising then the consumption of cold water helps to lower your core temperature. There are also sporadic claims that you absorb cold water slightly faster than warm water. Several places state this as fact, although I can't find a good reference for the statement. It doesn't appear to really mater what temperature the water is for normal hydration as it all eventually gets absorbed into the body. Absorption rates vary and it appears that no solid research has been done on this subject. There is a lot of guessing, but for exercise the consensus appears to be that cold water is probably the best. Also, properly hydrating the day before strenuous exercise can increase endurance. Before summing things up, there is an article in “Medicine & Science in Sports & Exercise”, April 2010 - Volume 42 - Issue 4 - pp 717-725. It says, “Compared with cold water, ice slurry ingestion lowered pre exercise rectal temperature, increased sub maximal endurance running time in the heat and allowed rectal temperature to become higher at exhaustion.” How would you like to be that athlete: before and after running your ass off they stick something up it. Not a good day!!!!

To summarize: measure the volume of your urine, make sure it is the right color, only drink one hour before and after a meal, on hot days drink cold water, 2-3 times each week drink hot water to purify your body, and drink ice slurry if you plan on exercising on a hot day.