Coffee Can Mess Up Your Body's Internal Clock

First Posted: Sep 16, 2015 09:01 PM EDT

Coffee always seems to be in the news these days, with other benefits besides just perking us up in the morning. Yet what about those who just love a good cup of Joe at night?

New findings published in the journal Science Translation Medicine reveal that having coffee at night can mess up your body clock, otherwise known as your circadian rhythm. The findings revealed that the amount of coffee before bed delay sleep by about three hours before bedtime, inducing a 40-minute phase delay in roughly the 24-hour human biological clock.

"This is the first study to show that caffeine, the mostly widely used psychoactive drug in the world, has an influence on the human circadian clock," said Wright, a professor in CU-Boulder's Department of Integrative Physiology, in a news release. "It also provides new and exciting insights into the effects of caffeine on human physiology."

In this recent study, the team recruited two females and two males who went through a double-blind, placebo-controlled study through CU-Boulder's Sleep and Chronobiology Laboratory. Researchers tested the subjects under four main conditions, including the following, courtesy of the release: low light and a placebo pill; low light and the equivalent of a 200-milligram caffeine pill dependent on the subject's weight; bright light and a placebo pill; and bright light and the caffeine pill. They also collected saliva samples from each participant who was tested periodically during the study to examine melatonin levels, which are produced naturally via the pineal gland and directed by the brain's "master clock."

Findings revealed that those who received a caffeine pill under low-light conditions had a roughly 40-miute delay getting to sleep based on their circadian rhythm, when compared to those who received the placebo under low light conditions. Furthermore, the findings revealed that bright light alone and bright light combined with caffeine induced circadian phase delays in the test subjects that were close to 85 minutes and 105 minutes, respectively. Yet there was no significant difference between dim light/caffeine combination and the bright light/placebo combination.

In the end, there might just be one simple remedy, according to Wright: "Removing coffee from your diet or just having it in the morning might help you achieve earlier bedtimes and wake times."

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