The results of a preliminary and small study suggest that a cup of coffee at bedtime seems to disturb the natural internal clock of the body. Caffeine, which is found naturally in over 60 plants, including the coffee bean, tea leaf, kola nut and cacao pod, is considered the most popular drug in the world.

People across the world consume caffeine on a daily basis in form of coffee, tea, cocoa, chocolate, some soft drinks, and some drugs.

Researchers for their study analyzed five people who were studied for over a period of 49 days. The study participants were asked to drink a capsule of caffeine equal to a double espresso or a placebo capsule, three hours before their regular bedtime.

The amount of the caffeine was adjusted according to their body size. In addition to this these people were exposed to bright or dim light. People usually want to go to bed earlier when exposed to bright light.

Researchers during the study noted that the coffee seemed to push the body clocks of the study participants by 40 minutes. This was almost 50 % of the delay related to exposure to bright light.

CU-Boulder Professor Kenneth Wright, who co-led the study with John O’Neill of the Medical Research Council’s Laboratory of Molecular Biology (LMB) in Cambridge, said in a statement that this is the first study that showed caffeine effects cellular timekeeping in the human body.

The study is still under its preliminary stages and nothing has been confirmed about the effects of caffeine on the body’s internal clock during morning and during the day. Researchers said findings of the research need further research and confirmation.