A barista makes coffee using the pour-over method at Artifact Coffee in Baltimore. Benjamin Morris/NPR hide caption

itoggle caption Benjamin Morris/NPR

The bar at a surprise birthday party for Teen Wolf's Stephen Lunsford, presented by Monster Energy last November in Los Angeles. Todd Williamson/Invision/AP hide caption

itoggle caption Todd Williamson/Invision/AP

There might be much more caffeine than you think in those supplements you're taking. There also might be much less. Janine Lamontagne/iStockphoto hide caption

itoggle caption Janine Lamontagne/iStockphoto

The contents of a box of some of the new foods containing caffeine collected by the Center for Science in the Public Interest. Karen Castillo Farfán/NPR hide caption

itoggle caption Karen Castillo Farfán/NPR

Sarah Piampiano holds two energy gels, one with caffeine and one without, as she runs in this year's Ironman World Championship. Murray Carpenter for NPR hide caption

itoggle caption Murray Carpenter for NPR

Bring on the caffeine — maybe. antwerpenR/Flickr.com hide caption

itoggle caption antwerpenR/Flickr.com