The saying goes that you are what you eat. Some may extend that to what you drink, too.

Whether you believe that old adage or not, scientists at the University of Utah and homicide detectives say that, at the very least, what a person drinks says a lot about where that person has been.

In a new study published today in the "Proceedings of the National Academy of Sciences," scientists at the U. outline a new procedure they have developed that can tell where a person has been based on isotopes in the water found in people's hair.

For their research, scientists analyzed the tap water and hair samples (collected from the floors of barber shops) in 65 cities and 18 states across the U.S. What they found was the isotopes in water vary from region to region. The difference would not be noticed from state to state, according to scientists. But a person who drinks water in Utah would have different isotopes in their hair than a person in Texas, scientists say.

This new procedure is expected to be beneficial not only to anthropologists and archaeologists, but also to homicide detectives, including cold case investigators.

"I think it'll be a huge breakthrough for missing persons investigations," said Salt Lake County Sheriff's detective Todd Park, who heads the cold case unit.

The longer a person's hair is, the more history it can tell about where that person has been.

"I walk around with about six or seven months of history," said the short-haired James Ehleringer, a biologist at the U. who helped lead the study. "(My wife) has about three years' worth of history."

Hair grows at an average rate of a half-inch per month, said Ehleringer.

"Basically we have come up with a technique that will allow law enforcement to get an idea of the travel history of an unidentified murder victim," he said. "The water and food you drink in a region gets recorded in the isotopes of your hair. So when you move from a region to the next, the isotope in your hair changes."

Already, the sheriff's office has put the new technique to use.

In October 2000, the skeletal remains of an unidentified woman were found near Saltair. In addition to bones, a white sock, a T-shirt, a blue choker-style necklace and hair were found. The woman was dubbed "Saltair Sally" and to this day has remained unidentified. Investigators believe the woman was between 16 and 20 years old. She was 5-foot-2 and had waist-length brown hair.

Park recently put some of those hair samples through the U.'s new test.

"It was able to give me a geographical location of where she had been the last two years of her life," he said. "That's significant to me. It narrows down my search."