Caffeine is commonly found in coffee, which is already a part of people's daily lives. However, taking it at night may not only kick the person awake, it may also disrupt the individual's internal body clock.

Kenneth Wright, a sleep and circadian physiologist at the University of Colorado, Boulder, conducted a study which involved allowing the five participants to take a pill containing caffeine equivalent to two shots of espresso three hours before bedtime. The study took 49 days.

Results from the study published, Wednesday, in journal "Science Translational Medicine," revealed that the release of melatonin, a hormone that normally rises during night time and is also an indicator of the internal clock — also known as circadian rhythm — was delayed by about 40 minutes, NPR reported.

"We found that caffeine did indeed, in the evening, shift your clock later," Wright said. "What we're seeing here now is another way that caffeine impacts our physiology that we didn't know about before in humans."

The study aims to find out and understand how the human body clock is being affected by caffeine, and the findings suggest that the substance is affecting the signalling within the cells, thus, creating a disruption on the "core component" of the cellular circadian clock, NewsHealth.com learned.

"We think this is another reason why we may have some sleep disruption," Wright told Live Science.

The researchers said that the study may have implications for people who are used to sleeping late at night and would like to get up early, or for those people experiencing jet lags after travelling from one time zone to another.

Jamie Zeitzer, assistant professor of psychiatry and behavioral sciences at Stanford University, reportedly complemented the study. He added, though, that the number of people who participated in the study are too small, thus making it hard for the findings to be applied to people in general.