In Dallas, where I live, summer is brutally hot. Down here, we're constantly looking for ways to stay cool: air conditioning, fans, spray bottles, canopies, you name it. But many of us neglect one of nature's best cooling systems -- perspiration.

During hot summers and intense exercise, sweating controls your body's temperature. But you have to supply plenty of water. In fact, because the body is 60% water, proper hydration is vitally important in more ways than many people realize.

Adequate water is necessary in every living cell to regulate chemical reactions. Water helps the body break down and absorb nutrients from foods. It cushions tissues, lubricates joints and transports waste products to the kidneys, where they're eliminated in urine. And it helps bowel function: In some people, simply drinking more water ends constipation.

Unfortunately, many of us don't get enough water. Women might cut back to avoid long lines in public restrooms. Men with prostate enlargement (which increases frequency of urination) often restrict fluids to help them sleep through the night. Kids don't stop playing to run to a drinking fountain. Busy adults don't interrupt work to fill a glass.

By the time you feel thirsty, you're already in water deficit.

How much water we need is determined by how much we lose through urine, perspiration and respiration. Generally, people should drink at least 6 to 8 cups of water daily. Because I work out a lot, I drink far more, closer to 14 cups.

Your need increases if you sweat more, spend more time outdoors or exercise. Some studies show athletes can lose up to 8 pounds of sweat in an hour! The American College of Sports Medicine recommends drinking 500 milliliters (just over 2 cups) of water two hours before a prolonged bout of outdoor exercise, and another 500 milliliters 15 to 20 minutes before exercise. While working out, drink at regular intervals to replace water lost in sweat.

Right now I imagine many of you trying to figure out whether you need to buy measuring cups. Relax. Just pay attention to your body. As you become dehydrated, your kidneys reabsorb as much water as possible, which concentrates the urine, darkening it. If you're adequately hydrated, the kidneys don't concentrate the urine as much, so it remains diluted and clear. When my patients ask me whether they need to drink more water, I just tell them to look at their urine. If it's diluted, their body is happy. If it is concentrated, their body wants more water.

One caveat: Many people think tea, coffee and caffeinated colas are as good as water at replacing fluid. Not so! Caffeine is a diuretic, which means it decreases the kidneys' capacity to concentrate urine. Consequently, tea, coffee and colas lead to dehydration, in spite of urine that appears diluted. (Alcohol and prescription medicines called diuretics have the same effect.) So, if you drink caffeine, limit it to two servings a day. Also, remember that those caffeine drinks don't count when tallying your daily water intake. And don't go wild with the ice: 40- to 50-degree water is best.

A few simple hydration habits

Make it convenient. I keep a 36-ounce mug in my desk drawer at work. When I get to the office in the morning, I fill the mug with water and drink it all before seeing my first patient. I repeat that at lunch and before I go home.

Make it tasty. A lot of people say, "Tedd, I would drink more water, but I don't like it!" Easy solution: Add a slice of lime, lemon or orange, or even a sprig of mint, for a desirable flavor.

Take it with you. Convenience stores have racks of refrigerated, bottled waters. Take advantage.

Drink in airplanes. It's possible to lose up to a pint of water during every hour of air travel. Frequent fliers say drinking ample water makes the trip better. Limit or eliminate caffeine and alcohol. Dehydration increases the risk of clots in the leg veins while flying.