Water: The Secret Ingredient of Good Health

While you may not consider water a nutrient, it's actually the most critical one in your diet. Okay, let's face it: many of us think there's nothing more boring than a plain old glass of water. But water serves a greater purpose than simply quenching your thirst. Did you know that blood is 85 percent water and that water also makes up 75 percent of your brain and 70 percent of your muscles? Water is behind all kinds of essential functions: it keeps you cool, helps you digest food, lubricates your joints, cushions your insides, and washes out wastes.

Even if you spend more time in the lounge chair than on the tennis court, you're still losing enough water each day to fill eight or ten glasses. Water sneaks out of your system without you noticing; you lose some just by breathing out. That's why you hear so much about the "eight glasses a day" rule. That's eight to ten 8-ounce glasses, folks. Most of us drink less than half that much!

A lot of people walk around in a state of chronic dehydration, and feel fatigue from that. Then they drink coffee for a little boost—however coffee further dehydrates you.

You may need even more than eight glasses a day, depending on what you're doing and where you are. If you live in a warm or dry climate or at a high altitude, or if you breathe dry air from a heater, dehumidifier, or air conditioner, your fluid loss increases dramatically. Plane travel also induces water loss: during a three-hour flight, you can actually lose one-and-a-half pints of water. Even a sunburn can increase water loss.

One way to tell if you're drinking enough is to do a quick check when you visit the bathroom. Lots of pale yellow urine is good; small amounts of dark urine mean more trips to the water fountain are in order. If you're pregnant or breast-feeding, or if you're postmenopausal, it's especially important to tote that water bottle. If you have kids along, be sure to share; they need extra water, too. Drink water before, during, and after exercise.