Federal health regulators are reviewing a Mars Wrigley chewing gum with added caffeine to find out how the stimulant affects children. The FDA Michael Taylor says Alert Energy gum is the latest in a line of foods that have added caffeine. The gum has 40 milligrams of caffeine in each piece, which is like drinking half-a-cup of coffee. Wrigley says the gum is being marketed to adults 25 and older. It says it welocomes the chance to work with the FDA on the subject.