Your body absorbs about half of the caffeine in your cup in seven minutes, explains Frank Ritter, Ph.D. who developed Caffeine Zone—an app that helps you monitor your body’s caffeine levels. And if you drank 200 milligrams (mg)—about the size of a small premium coffee—you’ll have absorbed 187.5 mg after 28 minutes. You’ll probably remember more from that morning meeting, too. Caffeine activates your sympathetic nervous system and stimulates the release of norepinepherine, a stress hormone that helps raise blood pressure and increase heart rate. The chemical sends a signal to your brain that something important is happening, and prompts your brain to store that information for later, explains Michael Yassa, Ph.D., a professor of psychological and brain sciences at Johns Hopkins University. When’s the right time for your a.m. jolt? Yassa recently conducted a study that showed that consuming 200 mg of caffeine five minutes after learning something enhanced memory for at least 24 hours.
Enhance performance with a small caffeine boost an hour before your workout
Caffeine has been shown to improve muscle strength and endurance, which is why you see runners downing coffee before a race. You’ll see this benefit by consuming low-to-moderate doses of caffeine—considered 3 to 6 mg per kg of body weight—15 minutes to one hour prior to exercise, according to a review paper in the Journal of the International Society of Sports Nutrition. If you’re a 170-pound guy, that’s between 213 and 463 mg of caffeine—roughly the amount found in a tall and venti Starbucks coffee, respectively. But cap it there: Downing higher amounts will not have you running like a track-and-field star. You’ll only increase your risk of suffering caffeine side effects, like the shakes.
Quit at noon
Think you can brew a pot in the p.m. and still be fine? You may be duping yourself. When normal sleepers were given 400 mg of caffeine before bed—either six hours, three hours, or immediately before—all of them saw their sleep suffer, a small study in the Journal of Clinical Sleep Medicine found. Strangely enough, these drinkers were unable to detect the sleep-wrecking effects of caffeine, possibly because nighttime awakenings can be difficult to notice, says study author Christopher Drake, Ph.D. Cut yourself off at least 6 hours before bed.