You may think you know the importance of adequate water intake, but recent research bucks conventional wisdom about how much people need to sip to stay healthy. Compare your knowledge with current findings on proper hydration.

  1. Should you let thirst guide your drinking habits?
  2. Can you eat your water?
  3. Is it possible to drink too much water?
  4. Do you need to drink more water when you exercise?
  5. Should everyone drink eight 8-ounce glasses of water a day?

1. No, according to Tammy Baker, RD, of Scottsdale, Arizona, who cautions against relying on thirst: “Usually, you are already partially dehydrated when you get thirsty.” A better benchmark of hydration is the color of your urine, she suggests. “If it’s pale lemonade color or lighter, you are hydrated. If it is dark yellow, you need more fluids.” Most experts agree with Baker’s logic, but one recent study in the American Journal of Physiology (2002, vol. 283) found that thirst sets in when the blood concentration of water (an accurate hydration indicator) has risen by less than2 percent and well before dehydration starts at 5 percent. So, according to this research, thirst could be an accurate guide for your drinking needs.

2. Yes. Consuming fruits, vegetables, soups, milk, juice, and even caffeinated beverages contributes to hydration, says Cedric Bryant, PhD, FACSM, chief exercise physiologist with the American Council on Exercise. In fact, you can cover about one-third of your required daily fluid intake from foods and drinks other than water because most green leafy vegetables contain more than 90 percent water, most fruit has more than 80 percent water, grain products are about one-third water, and protein food sources, such as meat, fish, or chicken, are up to two-thirds water.

3. Yes, it’s possible to overdose on water. A study in the British Medical Journal (2003, vol. 327, no. 7407) showed that athletes who pump themselves full of water or sports drinks may suffer overhydration, a life-threatening condition that results in low sodium concentrations in the blood, which is as dangerous as dehydration.

4. Yes. Basically, the more calories you burn, the more water you lose, explains Baker—about 1 tablespoon of water for every 15 calories burned. Aim to drink 2 cups of water for every pound lost during exercise. Or follow Bryant’s general guidelines: Drink 8 to 16 ounces of fluid at least one hour before you start exercising; drink 4 to 8 ounces of fluid every 10 to 15 minutes during exercise; and drink 16 to 24 ounces during the 30 minutes after exercise.

5. No. Recent findings from the Dartmouth Medical School indicate there’s no solid foundation for recommending eight 8-ounce glasses of water a day, because individual needs vary. For example, women need eight to ten glasses of water per day, and men need 12. Despite their small stature, children need more water because they lose 15 percent of fluid per day. For example, a 15-pound child needs to consume 34 ounces of water per day, but a 150-pound adult male needs to drink three times as much despite weighing 10 times as much. (Adults lose 4 percent of fluid per day.) Pregnant women need to make sure they get at least eight 8-ounce glasses a day during pregnancy, and lactating women need an extra 25 to 34 ounces (three to four additional glasses of water) during the first six months of lactation, according to World Health Organization guidelines.