Water comprises approximately 60 percent of your body weight and is needed for most bodily functions including sustaining cellular health, maintaining blood fluidity, cooling the body by sweating, eliminating waste products, moistening skin and mucous membranes, lubricating joints and aiding digestion. The amount of water you need to stay adequately hydrated varies depending on your health, circumstances and lifestyle. If you have questions about how much water your should be drinking for your specific activities and condition, consult your health care provider.
Three Basic Rules
The easiest way to remember your water needs is by using the "8 x 8" rule -- drink eight 8 oz. glasses, or approximately 1.9 liters, or 1900 milliliters, of beverages a day. The Institute of Medicine advises that men consume roughly 3 liters, or about 13 cups, of total beverages a day and women consume 2.2 liters, or about 9 cups, of total beverages a day. According to the "replacement approach," adults excrete 1.5 liters a day of water as urine and another liter through breathing, sweating and defecation. Since adults consume an average of 400 ml of fluid in food, they need to drink 2100 ml of beverages daily to replace lost fluids.
Increased Water Needs
Certain activities and conditions increase your need for water. You need more fluids when you are on a high protein or high fiber diet. Also, drink more fluids when you are outside in very hot weather or when you are sweating due to heat, intense exercise or fever. You also need extra fluids when you are outdoors at high altitude and in cold weather, especially if you are active. Skiers and mountain climbers don't feel thirst acutely in the cool dry air and may end up getting dehydrated if they don't pay attention to fluid consumption. Breastfeeding women should consume an additional 750 to 1,000 ml each day. Be especially careful on airplanes; the air is so dry that you can lose 1/2 liter of water an hour during a flight.
Dehydration
Symptoms of dehydration include headaches, fatigue, weakness, mood changes, slowed reactions, dry mucous membranes, confusion, and dark-colored urine. Particularly at risk for dehydration are the very young, the elderly and the sick.
Drinking Too Much Water
Drinking so much water that you decrease the sodium concentration in your blood to unsafe levels causes water intoxication, or hyponatremia. Symptoms include headaches, blurred vision, cramps, brain swelling and coma. Hyponatremia is relatively rare. At risk are infants fed overly diluted formula, people with certain illnesses or chronic conditions and endurance athletes who lose salt by sweating and then replenish water but not electrolytes. Athletes should drink no more than 1 liter per hour of plain water during extended exercise.
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