One late night? Coffee has your back the next morning. That double latte will even help perk you up after two nights of binge-watching in a row. But after that, you’re on your own, according to a new study from scientists at the Walter Reed Army Institute of Research. Sadly, they found that caffeine does zilch to boost alertness or performance after three nights of restricted sleep.
Forty-eight study participants racked up just five hours of sleep for five nights running (ideally, you need seven to eight). Some were given a 200 mg jolt of caffeine (about the amount in a short Starbucks coffee) twice during the day, while others received a placebo. A series of cognitive tests found that the caffeinated folks performed better on the first and second days, but after the third night, the buzzy benefits were gone.
General Health Magazine 