Mother Jones has published a March 5, 2014, interview with journalist Murray Carpenter about his forthcoming book, Caffeinated: How Our Daily Habit Helps Us, Hurts, and Hooks Us, which aims to “bring[] us the inside perspective at the additive that Salt Sugar Fat overlooked.” speaking with Maddie Oatman about “how much caffeine is healthy, where the industry stands on labeling, and  the most pretentious coffee preparation he’s observed,” Carpenter notes that current regulations do not require foods or supplements to disclose caffeine content on labeling.

“There’s some voluntary labeling initiatives underway: The American Beverage Association has recommended bottlers do that, but you can still find energy drinks that don’t tell you how much caffeine is in them,” Carpenter is quoted  as saying. “It’s not impossible for coffee and tea to start doing this. And for the products where caffeine is blended in very specific amounts, I don’t see any reason consumers should be left in the dark.”

In particular, Carpenter reports that “a healthy daily dose of caffeine” varies from person to person, depending on age, size, and other genetic factors that can influence caffeine metabolism. But he stops short of issuing a straight- forward answer on the overall health impact of caffeine consumption. “This is the question I got all the time: What’s the verdict? Is it good or is it bad?,” concludes Carpenter. “If I had a simple answer, it would have been a five-page book. It can be more effective than I had any idea, in terms of improving your alertness, your cognition, your athletic ability. It can have stronger more acute effects on sleep and anxiety than I’d imagined. It can be terrific. I think it’s important that everybody recognize how much is good for them, what it does for them when they take it, what they feel like when they don’t take it, and experiment.”