Various $4 affect your health in different ways - a new study shows coffee $4, while many energy drinks have surprisingly $4.
Caffeine itself is a stimulant with some positive and negative effects. It makes most of us feel more alert, awake, and focused, but too much can also backfire.
It also affects a host of processes in our bodies, including our digestion, metabolism, and vision.
Here's what's really going on after you drink a cup of joe.