When tea is digested, its caffeine molecules bind to more stable, larger molecules, such as catechins. This slows the breakdown of caffeine in the bloodstream and creates a time-release effect. This counteracts the negative side effects of caffeine, which in coffee can lead to cortisol production. Cortisol is the stress hormone that pushes your nervous system into flight or fight mode to create the anxiety, nervousness and jittery paranoia needed to flee or take on a threat. Experiencing this on a daily basis? Probably not a good idea. Cortisol also leads to weight gain.