Water makes up more than two-thirds of our body weight. The brain is 95 percent water, the lungs 90 percent and the blood 82 percent.

That explains why as little as a 2 percent drop in body water can lead to headaches, fatigue and dizziness. When clients complain of low energy, my first question is about water intake. Water also hydrates skin and joints and helps some people control appetite.

Water’s central role in good health lies behind a program I learned about at the recent Academy of Nutrition and Dietetics annual meeting in Philadelphia. Called Take Back the Tap, its aim is to encourage people to drink tap water — a move that will save them money and spare the environment.

Americans spent $10.6 billion on bottled water in 2009 — a phenomenal outlay for something that is freely available. The energy used to produce and transport plastic water bottles in 2007 would fuel 1.5 million cars for a year. And about 75 percent of empty plastic water bottles end up in landfills, lakes, streams and oceans.

It’s a myth that bottled water is somehow healthier than tap water. There is, in fact, more frequent and vigorous government testing of municipal water than bottled water.

If you don’t like the taste of tap water, filters are an option. Carbon and charcoal filters are good for chlorine and flavor issues.

As for contamination, distillation and reverse-osmosis filters can handle arsenic, perchlorates and lead. Consumers receive a water quality report each July 1 that lists all contaminants in their water. More information on water safety is available at water.epa.gov/drink.

Reusable water bottles come in stainless steel, BPA-free plastic and glass. Myriad choices in shape, spouts and color assure a good fit for everyone. Drink refreshing tap water for the sake of your body and your wallet.

Sheah Rarback is a registered dietitian on the faculty of the University of Miami Leonard M. Miller School of Medicine.