July health news: Myths about how much water you should drink

How much water do you need?
Myths aside, you do lose water every day through your skin when you sweat and through your urine, and you do need to replace that water because it's crucial for your body to function well. "That's the purpose of the thirst mechanism," says Goldfarb. "It tells us even when we are having the earliest stages of water decline. That's when we need to drink."

Rehydrate with water, coffee, tea, juice and fluids in food. (Water depletion by drinking coffee or alcohol is also a myth, adds Goldfarb). Aim for about 2.5 quarts for women and about 3 quarts for men per day. Drinking more than a quart an hour can lead to serious illness. "You can die," says Goldfarb. "You can have brain swelling because the water accumulates in the body and you're taking it in faster than the body can excrete it."

Should I drink more water when I exercise?
Even during exercise, it's fine to follow your thirst. In fact, Goldfarb says people over-drink during exercise. "More people have been hurt by drinking extra amounts of water during severe exertion. Marathon runners are cautioned to reduce their water intake and not to drink excessively, as they become quite ill from diluting their body fluid."

So who needs extra water? People with kidney stones -- they need to dilute the stone-forming constituents that come out in the urine -- and people who are exposed to very hot environments -- working outdoors in hot weather or indoors in heavy protective clothing, for example, as they lose more water through their skin when they sweat.

For the rest of us, mild dehydration or mild over-hydration is OK. Drink to quench your thirst, not to prevent health and/or beauty issues. "There are things that we do know are better for our health like stopping smoking, losing weight and exercising," says Goldfarb. "You shouldn't think that drinking lots of water is going to substitute for those things that we do know are beneficial." 

How do other liquids affect your body? Learn about the health effects of red wine and how to drink to protect your heart.

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