Coffee, tea, soda, Red Bull, those little something-extra mints ... whatever your caffeine-delivery system of choice, maybe you should stick with it -- especially if you work nights or odd shifts.

In a review of 13 previously published studies on caffeine's effect on shift workers' performance, researchers found that, compared with a placebo or even naps, the stimulant appeared to be more effective at reducing errors. It also boosted performance on memory, attention, perception and reasoning tests.

Not bad for something available from a vending machine.

Here's the short version of the caffeine study, published Wednesday in the Cochrane Library.

And here's how caffeine affects the brain, courtesy eHow, and a look at caffeine chemistry, courtesy About.com.

But good luck choosing a drink or food based on the caffeine content listed on the label. It doesn't have to be there.

Consumers can do their own research on caffeine content over at Energy Fiend. They can even calculate how much of their favorite product they could consume before it would likely prove fatal. (In the case of Cherry Coke, at least, this is a considerable amount.)

-- Tami Dennis

Photo credit: Los Angeles Times