This is why you should use an ear piece when chatting on the phone.

The report said it was unclear whether the changes in the brain — an increase in glucose metabolism after using the phone for less than an hour — had any negative health or behavioral effects. But it has many people wondering what they can do to protect themselves short of (gasp) using a landline.

“Cellphones are fantastic and have done much to increase productivity,” said Dr. Nora Volkow, the lead investigator of the study and director of the National Institute of Drug Abuse at the National Institutes of Health. “I’d never tell people to stop using them entirely.”

Yet, in light of her findings, she advises users to keep cellphones at a distance by putting them on speaker mode or using a wired headset whenever possible. The next best option is a wireless Bluetooth headset or earpiece, which emit radiation at far lower levels. If a headset isn’t feasible, holding your phone just slightly away from your ear can make a big difference; the intensity of radiation diminishes sharply with distance. “Every millimeter counts,” said Louis Slesin, editor of Microwave News, an online newsletter covering health and safety issues related to exposure to electromagnetic radiation.