How Much Caffeine Is Too Much?

To some, “but first, coffee” isn’t just a trendy turn of phrase; it’s a motto to live by. And while caffeine, in general, has been linked to a number of health benefits—from improved exercise performance to boosted brainpower—it is possible to have too much caffeine.

Refresher: Caffeine is a stimulant, meaning it triggers activity in your central nervous system that can lead to increases in heart rate and blood pressure, among other side effects, according to the National Library of Medicine.

Caffeine also blocks adenosine receptors, aka central nervous system depressants in the brain that, normally, make you feel tired and induce sleep, says Robert Glatter, M.D., an assistant professor of emergency medicine at Lenox Hill Hospital, Northwell Health. By blocking them, caffeine wakes you up (and gives you that I-can-do-anything superhuman feeling), he explains.

Excerpted from Shape

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