Water doesn't get the same media attention as green tea, antioxidants, and the latest fad diets. Yet it plays a much more critical part in our daily lives and our bodies.

Our bodies are made up of about 60% water, and every system depends on water. So water is important for healthy skin, hair, and nails, as well as controlling body temperature, heart rate, and blood pressure.

"It's definitely essential," says Jim White, registered dietitian and personal trainer in Virginia Beach, Va., and American Dietetic Association spokesman.

"What we're finding is so many people are deficient," he notes. "We're seeing a huge decrease in athletic performance and fatigue that's caused by the lack of hydration."

You can stay fully hydrated throughout the day by drinking water and other fluids, as well as eating foods that are hydrating.