Although no single formula fits everyone, knowing more about your body's need for fluids will help you estimate how much water to drink each day.
Health benefits of water
Water is your body's principal chemical component and makes up about 60 percent of your body weight. Every system in your body depends on water. For example, water flushes toxins out of vital organs, carries nutrients to your cells and provides a moist environment for ear, nose and throat tissues.
Lack of water can lead to dehydration, a condition that occurs when you don't have enough water in your body to carry out normal functions. Even mild dehydration can drain your energy and make you tired.
How much water do you need?
Every day you lose water through your breath, perspiration, urine and bowel movements. For your body to function properly, you must replenish its water supply by consuming beverages and foods that contain water.
So how much fluid does the average, healthy adult living in a temperate climate need? The Institute of Medicine determined that an adequate intake (AI) for men is roughly 3 liters (about 13 cups) of total beverages a day. The AI for women is 2.2 liters (about 9 cups) of total beverages a day.
Factors that influence water needs
You may need to modify your total fluid intake depending on how active you are, the climate you live in, your health status, and if you're pregnant or breast-feeding.
- Exercise. If you exercise or engage in any activity that makes you sweat, you need to drink extra water to compensate for the fluid loss. An extra 400 to 600 milliliters (about 1.5 to 2.5 cups) of water should suffice for short bouts of exercise, but intense exercise lasting more than an hour (for example, running a marathon) requires more fluid intake. How much additional fluid you need depends on how much you sweat during exercise, and the duration and type of exercise. During long bouts of intense exercise, it's best to use a sports drink that contains sodium, as this will help replace sodium lost in sweat and reduce the chances of developing hyponatremia, which can be life-threatening. Also, continue to replace fluids after you're finished exercising.
- Environment. Hot or humid weather can make you sweat and requires additional intake of fluid. Heated indoor air also can cause your skin to lose moisture during wintertime. Further, altitudes greater than 8,200 feet (2,500 meters) may trigger increased urination and more rapid breathing, which use up more of your fluid reserves.
The question: I've heard the rumor that you should drink water to lose weight. But can simple H20 really help you shed pounds? It sounds too good to be true.
The experts: Brooke Alpert, R.D., founder of B Nutritious, and Keri Peterson, M.D., a physician at Lenox Hill Hospital in New York City and a medical advisor for Women's Health
The answer: "I don't think that water directly affects weight loss," says Alpert. "However, I think water consumption is directly correlated with weight loss." As in: Water does not have some magical property that burns fat (sorry!), but it definitely can help you with your weight-loss efforts (hooray!).
First off, staying hydrated could help you avoid overeating. "A lot of people confuse thirst for hunger," says Peterson. "So they'll tend to eat rather than drink water." If you're craving a midday snack and want to make sure your pangs are caused by hunger, not hydration, have a glass of water first. Then see if you're still hungry 30 minutes later, says Peterson.
Also important to keep in mind: "If you're continually staying well hydrated, that false cue won't happen," says Peterson. To make sure you're getting enough H20 in general, the key is your pee (seriously): You want it to be a pale yellow.
Of course, drinking water also means you're not drinking something else—such as sugary, caloric beverages or even potentially diet-breaking diet soda.