How much water should I drink each day?
You've probably heard that adults should consume eight glasses of water every day. But, c'mon, when was the last time you kept track? Most people drink … well, when they're thirsty. Because you do need to replace the fluids you lose through sweating, exhaling, exercise, and more, the Institute of Medicine of the National Academies recently suggested that women should take in 91 ounces (or about 11 cups) of fluid, and men should get about 125 ounces (around 16 cups) on a daily basis.

How can I tell if I'm getting enough water?
Because all people are different—in size, exercise habits, and sweat rates—it's hard to come up with a one-size-fits-all recommendation. One of the best indicators of overall hydration, says Nancy Clark, a Boston-based registered dietitian and sport nutritionist, is to monitor your urine frequency and output. "People should be urinating every two to four hours," she says. "If it's a light color and significant volume, that means you're getting plenty of fluids. But if you go from 8 a.m. until 3 p.m. without having to take a bathroom break, and then when you do, your urine is really dark and concentrated, that's a sign you're dehydrated."

Can I eat my daily water requirement?
Believe it or not, you can get your daily water requirement without ever drinking a glass of water. The water in foods you eat and all of the liquids you drink count toward your daily total. On average, about 20 percent to 30 percent of daily water needs come from food, and fluids provide the remaining 70 percent to 80 percent. "An orange is 90 percent water," says Clark. "Lettuce is mostly water. Soup is water. Yogurt even contains water."

Is bottled water purer than tap water?
It depends. Two government entities regulate water: The U.S. Food and Drug Administration (FDA) for bottled, and the U.S. Environmental Protection Agency (EPA) for piped tap water supplied by public sources. The EPA requires that all public suppliers provide customers with annual water quality reports, but that doesn't mean tap water is always pure.

A 2005 survey conducted by the Environmental Working Group found 260 contaminants in tap water from 42 different states. Bottled water quality varies by brand. Whether buying water is worth it may depend on where you live, lifestyle needs (bottled water is portable), and taste. To learn more about bottled water and tap water rules, contact the FDA (www.fda.gov) or a regional EPA office (www.epa.gov).

Is oxygenated water for real?
According to Susan Bowerman, a registered dietitian and assistant director of the Center for Human Nutrition at the University of California, Los Angeles, increasing water's oxygen content is just not possible. "Water is defined as having two hydrogen atoms and an oxygen, so as far as water that is touted as 'super-oxygenated water,' no, there is no science behind that," says Bowerman. "Water is water." Even so, some oxygenated water companies, such as Penta, claim that adding oxygen at the end of a 13-step purification process helps preserve a clean, crisp taste.

Do "fortified" waters have merit?
Next to the shelves lined with spring water, purified water, and sparkling water is a new category of H2O: products fortified with a potpourri of nutrients, natural and artificial flavors and colors, caffeine, and even fiber. Manufacturers claim these can do everything from boost energy and calm nerves to help people lose weight. Do they work? Many dietitians are skeptical. If you're taking a daily multivitamin already, there's no reason to drink vitamin-enhanced drinks, says Bowerman. But if you're not popping a daily multi, the vitamin-enhanced drinks could help supply you with essential nutrients. You may get more sugar with this mode of delivery—but if the natural flavor encourages you to drink more, it's probably not the worst thing as an occasional indulgence.