Midafternoon slump: I need one cup of coffee and two chocolate-chip biscuits. The original fresh-brewed brain fuel. In one study, British researchers found that those people consuming the caffeine equivalent of approximately one cup of coffee experienced improved attention and problem-solving skills.

Try two chocolate-biscuits or half a Danish. "The fat in foods like these triggers the release of cholecystokinin, a hormone that slows stomach emptying, which may help maximise your absorption of caffeine," says John Allred, Ph.D., a professor of food science.

Just stop at one coffee though; another study found that men given more caffeine did worse on attention tests.