WASHINGTON » Trail mix. Potato chips. And now gum.

With a growing number of foods boasting added caffeine for an energy boost, the Food and Drug Administration says it’s time to investigate their safety.

The FDA’s new look at added caffeine and its effects on children and adolescents is in response to a caffeinated gum introduced this week by Wrigley. Called Alert Energy Gum, it promises "The right energy, right now." The agency is already investigating the safety of energy drinks and energy shots, prompted by consumer reports of illness and death.

Michael Taylor, FDA’s deputy commissioner of foods, said in a statement today that the only time FDA explicitly approved the added use of caffeine in a food or drink was in the 1950’s for colas. The current proliferation of caffeine added to foods is "beyond anything FDA envisioned," Taylor said.

"The environment has changed," he said.

Taylor said the agency will look at the potential impact these "new and easy sources" of caffeine will have on children’s health and will take action if necessary.

Wrigley and other companies adding caffeine to their products have labeled them as for adult use only. A spokeswoman for Wrigley, Denise M. Young, said the gum is for "adults who are looking for foods with caffeine for energy" and each piece contains about 40 mg, or the equivalent amount found in half a cup of coffee. She said the company will work with FDA.

"Millions of Americans consume caffeine responsibly and in moderation as part of their daily routines," Young said.

Food manufacturers have added caffeine to candy, nuts and other snack foods in recent years. Jelly Belly "Sport Beans," for example, have 50mg of caffeine in each 100-calorie pack, while Arma Energy Snx markets trail mix, chips and other products.

Critics say it’s not enough for the companies to say they are marketing the products to adults when the caffeine is added to items like candy that are attractive to children.

"Could caffeinated macaroni and cheese or breakfast cereal be next?" said Michael Jacobson, director of the Center for Science in the Public Interest, which wrote the FDA a letter concerned about the number of foods with added caffeine last year. "One serving of any of these foods isn’t likely to harm anyone. The concern is that it will be increasingly easy to consume caffeine throughout the day, sometimes unwittingly, as companies add caffeine to candies, nuts, snacks and other foods. "