How much water should you drink each day? ? a simple question with no simple answer. Various studies have produced recommendations over the years, but in truth, your water intake will depend on many factors, including where you live, your health, and your activity level.

Health benefits of water

The health benefits are fairly well known and not very profound. The human body is 55%-65% water, depending on age, sex, and overall health. On average, women have less water than men, and overweight people have less than thin people (fat tissue contains less water than lean tissue).

So 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.

There are generally two approaches:

* Replacement: The average urine output for adults is 1.5 liters a day. You lose close to an additional liter of water a day through breathing, sweating and bowel movements. Food counts for about 20% of our daily fluid intake, so consuming 2 liters of water will typically replace lost fluids.

* Dietary recommendations. The Institute of Medicine advises that men consume roughly 3.0 liters (about 13 cups) of total beverages a day and women consume 2.2 liters (about 9 cups) of total beverages a day.

It is generally the case that if you drink enough fluid so that you rarely feel thirsty and produce between one and two liters of colorless or slightly yellow urine a day, your fluid intake is probably adequate.

Factors that influence water needs

Your total fluid intake may need to be modified depending on how active you are, the climate you live in, your health status, and if you're pregnant or breast-feeding.

* Exercise. The more you exercise, the more fluid you'll need to keep your body hydrated. An extra cup or two of water should suffice for short bouts of exercise, but 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. Fluids should also be replaced after exercise.

* 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.

* Illness or health conditions. Signs of illnesses, such as fever, vomiting and diarrhea, cause your body to lose additional fluids. In these cases you should drink more water and may even need a sports drink to replace lost sodium.

* Pregnancy or breast-feeding. Women who are expecting or breast-feeding need additional fluids to stay hydrated. Large amounts of fluid are lost especially when nursing.

Dehydration and complications

Failing to take in more water than your body uses can lead to dehydration. Even mild dehydration can sap your energy and make you tired. Common causes of dehydration include strenuous activity, excessive sweating, vomiting and diarrhea.

Signs and symptoms of dehydration include:

* Mild to excessive thirst * Fatigue * Headache * Dry mouth * Little or no urination * Muscle weakness * Dizziness * Lightheadedness

Mild dehydration rarely results in complications ? as long as the fluid is replaced quickly ? but more-severe cases can be life-threatening, especially in the very young and the elderly.

Staying safely hydrated

It's generally not a good idea to use thirst alone as a guide for when to drink. By the time one becomes thirsty, it is possible to already be slightly dehydrated.

To ward off dehydration and make sure your body has the fluids it needs. Nearly every healthy adult can consider the following:

* Drink a glass of water with each meal and between each meal. * Hydrate before, during and after exercise. * Substitute sparkling water for alcoholic drinks at social gatherings.

If you drink water from a bottle, thoroughly clean or replace the bottle often. Refill only bottles that are designed for reuse.

Can you drink too much water?

Though uncommon, it is possible to drink too much water. When your kidneys are unable to excrete the excess water, the electrolyte (mineral) content of the blood is diluted, resulting in a condition called hyponatremia (low sodium levels in the blood). Endurance athletes who drink large amounts of water are at higher risk of hyponatremia. In general, though, drinking too much water is rare in healthy adults who consume an average American diet.

If you're concerned about your fluid intake, check with your doctor or a registered dietitian. He or she can help you determine the amount of water that's best for you.