Diets & Weight Loss
provides the environment in which cellular chemical reactions take place. The body has three sources of water: the fluid you drink, the water content of the food you eat, and the metabolism of proteins, carbohydrates and lipids.
Even if you're inactive, your body loses up to 80 ounces of water a day — mainly in urine, perspiration (even invisible sweat) and bowel movements. Every time you exhale, for example, you lose water vapor that adds up to 1 or 2 glasses of water a day. To replace this loss, you should consume at least 6 full glasses of water a day — a minimum of about 48 ounces. Of course, foods are 70% to 90% water, so don't count just the glasses you drink in a day.
The amount of water you need varies depending on the climate where you are and the amount of activity you engage in. For instance, intense exercise in hot, humid weather can cause excess water loss of a quart (32 ounces) or more an hour through sweat. That water must be replenished immediately to prevent serious dehydration, even death. If too much fluid is lost through sweating, blood pressure falls and the amount of oxygen getting to the brain decreases.
Here are a few guidelines to getting your daily fluid quota of six to eight glasses:
- Thirst is not always a good indicator of the body's need for water. It's important to drink regularly, even if you don't feel thirsty. This is especially true in the elderly because the sensation of thirst becomes weaker in very old people. Also, intense dehydration may impair the usual strong desire to drink.
- Drink 1 or 2 glasses of water 30 minutes to 1 hour before exercising. Drink a half of a glass again 10 minutes before your workout. Finally, drink at least 1 glass of water after you finish exercising.
- You don't need sports drinks, unless you do strenuous aerobic exercise for at least 60 minutes. These beverages contain sugar or fruit juice and electrolytes (mainly sodium and potassium). But for most of us, ordinary water is fine.
- Increase your fluid intake if your diet is high in fiber, protein or salt.
Remember, fluid comes in a variety of forms, including the water in solid foods. Many fruits, vegetables and soups are at least 80% water, so they can count toward your daily intake.
Milk, diet sodas, unsweetened carbonated waters, most herbal teas, decaffeinated teas and decaf coffee can substitute, cup-for-cup, for pure water. The same is no true of fruit juices and sugar-sweetened drinks. Although theses other beverages still count as fluid sources, there sugar content can slow down your body's water absorption.
Finally, don't count coffee or alcohol as a water substitute: Caffeine is a mild diuretic (a substance that helps remove water from the body via urine). This makes coffee and other caffeinated beverages poor sources of water.
It is possible, but very rare, for a healthy person to drink too much water to the point of toxicity. Even if you drink a great deal of water, there's no danger of flushing nutrients out of your body — or excess calories, for that matter. Nutrients dissolved in water are absorbed into the bloodstream from the digestive tract, long before water goes to the kidneys for excretion.
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