App Tells You When and How Much Coffee Is Right for You

It’s 2:30 p.m., and you’re wondering: Have a cup of coffee and perk up? Or will you be too wired to sleep that night?  

A new app can help demystify how much caffeine to consume—and when to consume it—to ensure that optimal wide-awake feeling without shredding your night’s sleep.

“Many people don’t understand how caffeine levels in their bloodstream go up and how they go down,” said Frank Ritter, professor of information sciences and technology, psychology and computer science and engineering at Penn State.

Ritter and other Penn State researchers have developed Caffeine Zone, a true “coffee talk” app, which integrates information on caffeine consumption and its effects to produce a graph of how the caffeine affects a user over the course of a day.

“It’s important to understand the effect that caffeine can have at these various levels,” Ritter said.

The point of the app is to help people determine when caffeine may give them a mental boost and when it could hurt their sleep patterns.



The app’s developers point out that that the speed at which caffeine is consumed is also important. If drunk rapidly, a cup of coffee can cause a spike in mental alertness, but enough of the drug can linger in the bloodstream to cause sleep problems hours later, said Ritter, who worked with Kuo-Chuan (Martin) Yeh, assistant professor of computer science and engineering.

People who drink too much caffeine too quickly may face other problems, the researchers said. A spike of caffeine above the optimal level can cause nausea and nervousness.

Peer-reviewed studies were used as input data to determine that caffeine drinkers with between 200 and 400 milligrams of caffeine in their bloodstream are in a zone of optimal mental alertness. For sleep, they set a lower threshold of 100 milligrams. Coffee drinkers may have sleep problems if they remain above this.

To plot caffeine’s effect, customize the app’s settings. First, unless you’re from the euro zone, find an online conversion to translate your weight into kilograms. Enter your weight. Choose your caffeine consumption and how quickly you drink it. There’s no choice for caffeinated sodas, but you can enter a custom caffeine dose. You can’t store custom settings, but the history will store them for you and they can be reused.

Then check the graph and watch the line creep up to the optimal green zone for alertness. When you want to make sure you’re set for sleep (the blue zone at the bottom of the screen), stop drinking caffeine. Or make sure your headphones are on: the app sends occasional alerts warning you when your caffeine is about to run low.

The app is available on iTunes for free with advertisements or for purchase without ads. It works only on Apple devices—the iPhone, iPod Touch and iPad.