Does your morning start only after your first (or second) cup of coffee or mug of tea? You're not alone: It’s estimated that 85% of U.S. adults consume caffeine, the world’s most widely used central nervous system stimulant. Most of those folks get their caffeine through coffee, but it’s also in chocolate, tea, soda pop, and even painkillers.
Caffeine shakes out the cobwebs, making you feel more mentally alert. But it can also disrupt your sleep or make you anxious or jittery, especially if you’re sensitive to it or consume too much.
“Clearly some people are more sensitive to the physiological effects of caffeine than others and would benefit from keeping coffee to a minimum or switching to a decaffeinated variety,” says Robin Poole, MB ChB, a researcher at the University of Southampton in the U.K., who has reviewed the health effects of coffee.
It’s worth noting, says Connie Weaver, PhD, distinguished professor in the department of nutrition science at Purdue University, that research to separate the benefits of coffee versus caffeine are lacking. In fact, recent research from the University of Southern California Keck School of Medicine tied both regular and decaf coffee consumption to a lower risk of death due to heart disease, cancer, stroke, diabetes, and respiratory and kidney diseases.
So how does caffeine specifically affect overall health? Studies point to a number of possible benefits and some risks. For most healthy adults, a daily dose of up to 400 milligrams of this widely used stimulant does not pose health risks, studies suggest. That’s roughly four small (5-ounce) cups of coffee–or upwards of 10 cups of tea.
If you’re wondering about your own caffeine habit, talk to your doctor about these potentially helpful and harmful effects.