Drinking coffee at night can prevent you from getting a good night sleep but caffeine does more than just keep you awake. It also messes with your body's internal clock that dictates when it is time to sleep and wake up.

Findings of a small and preliminary study, which was published in the journal Science Translational Medicine on Sept. 16, suggest that consuming caffeine before bedtime could disrupt the body's internal clock causing jet lag style sluggishness during the day.

Kenneth Wright Jr., from the University of Colorado at Boulder, and colleagues conducted an experiment with five people over a period of 49 days.

The participants were asked to consume either a capsule of caffeine equivalent to that of a double espresso or a placebo three hours before bedtime. The participants were also exposed to either dim or bright light, the latter known to reset the body's clock causing people to want to go to sleep later.

Wright and colleagues found that caffeine appeared to delay the body's internal clock by about 40 minutes, which is about half the delay associated with exposure to bright light.

The researchers said that caffeine delays the release of the sleep hormone melatonin and this disrupts the body's internal clock so that the beginning of the biological night is pushed to a later time.

It has long been known that caffeine causes the release of chemicals in the brain that promote arousal and wakefulness but the findings of the new study suggest that caffeine also affects the body by influencing the circadian rhythm.

"The circadian clock is way beyond 'sleep and wake,'" Wright said. "The circadian clock is present in cells throughout our entire body. It's in your fat cells; it's in your muscle cells. It's in your liver, for example, as well as in your brain."

Experts said that this kind of shift in the circadian rhythm could be enough to make people struggle to get up at the right time the next day albeit it remains unclear if drinking coffee earlier during the day could also mess with the body's inner clock in a similar manner.

Researchers said that the findings suggest that caffeinated drink at night may help explain why some people are "night owls." The findings likewise offer a prospect for using caffeine as treatment for jet lag since it appears capable of adjusting the body block.

Photo: David Pacey | Flickr

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