A new study shows that cell phones do have an affect on the glucose metabolism in the brain, but researchers still don't know whether that is dangerous.

A cell phone gives off energy, and when it's held to a person's ear, the study shows the brain reacts and is sensitive to the radiation.

The report in this week's Journal of the American Medical Association details the result of a year-long study by the National Institutes of Health of 47 cell phone users. They had study participants hold both a muted cell phone and a cell phone that was turned off up to their ear for 50 minutes.

For years, studies have tried to link cell phones and cancer but have been inconclusive. Medical experts say this new study could offer the first real step in the search for an answer.

"Unfortunately, our findings do not enlighten in any way this controversy on whether cell phones produce cancer. What they do say is that the human brain is sensitive to this electromagnetic radiation," said Dr. Nora Volkow, a director with the National Institutes of Health and lead researcher for the study. "Whether this electromagnetic radiation has any negative consequences, that is something that needs to be properly evaluated."

Joel Moskowitz, director of the Center for Family and Community Health at UC Berkeley told the San Francisco Chronicle he's not convinced that cell phones are dangerous, but he is frustrated with the pervasive refusal by many scientists to seriously consider the possibility. He hopes the latest study - and its association with the National Institutes of Health and publication in one of the country's major scientific journals - will give credibility to the need to look deeper.

"This study establishes that cell phones do indeed have biologic reactivity on the brain. The industry and scientific community seems reluctant to hear that," Moskowitz said. "I'm hoping this study will force policymakers to take this issue much more seriously and begin to encourage research in this area."