How high is too high? "Research shows that for most healthy people, consumption of up to 400mg of caffeine per day is safe," says Sarah Rueven, RD, MS, CDN, founder of Rooted Wellness. "This equates to about two to three cups of coffee. However, the caffeine content of coffee varies greatly depending on the source of the bean and preparation method." For someone with a mild habit, that sounds reasonable enough. But for someone with a more extreme consumption habit, well that's a different story.
To get back to basics, you might be wondering what exactly caffeine does to your body to help you stay alert when you're running on three hours of sleep. First off, how you're affected by caffeine can depend on age and genetics, which will determine how your body absorbs and metabolizes it.
"Caffeine enters the bloodstream and works as a stimulant as it binds to adenosine receptors in the brain," says Yasi Ansari, MS, RD, CSSD, a national spokesperson for the Academy of Nutrition and Dietetics. "Adenosine is a nervous system depressant. It promotes sleep controls and can affect memory and learning. When caffeine binds to these receptors, adenosine's effects are lessened and the body is instead stimulated; then it increases adrenaline, which gives the body a boost of energy!"
And energy isn't the only benefit of caffeine, the experts shared what you can feel good about when sipping your cup of joe (or tea):