Still, researchers wondered, does caffeine actually alter your body’s internal clock, your circadian rhythm?
Advertisement
“By understanding the effect caffeinated drinks have on our body clock, right down to the level of individual cells, gives greater insight into how we can influence our natural 24 hour cycle – for better or for worse”.
They were then given caffeine, the equivalent of a double espresso, or a placebo three hours before they went to sleep and were exposed to dim or bright light (the bright light acted as a control as it also delays the human circadian clock) to find out when the surge in melatonin occurred.
Properly timed caffeine use may also be of benefit with respect to shifting circadian timing, potentially assisting with circadian adaptation to large phase delays required when flying across many time zones westward, as well as sustaining wakefulness until bedtime in the new time zone.
Although most people will have experienced caffeine-induced insomnia, it appears that it is not only the chemical stimulating effect of the drink which causes sleeplessness.
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”.
The experts say they found atht caffeine can turn the clock back directly by activating a receptor protein “switch” found in all cells. It’s controlled by a region of the brain that regulates hormonal and neural activities that trigger certain bodily functions – like sleepiness and alertness – over a 24-hour period.
GREENFIELDBOYCE: Kenneth Wright is a sleep and circadian physiologist at the University of Colorado, Boulder. It’s in your fat cells.
GREENFIELDBOYCE: And irregularities in the circadian clock have been linked to everything from obesity to cancer. 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. The USA team studied five people to see when melatonin started to appear in saliva.
“These and other data clearly indicate that we can to some extent modify these rhythms and that part of the reason why we sleep so late relates to factors such as caffeine intake and the exposure to artificial light in the evening”, he said.
T.M. Burke et al., “Effects of caffeine on the human circadian clock in vivo and in vitro”, Science Translational Medicine, 7:305ra146, 2015. John O’Neill was on the team. The Medical Research Council and the Wellcome Trust also helped to fund the study.
Whether people who are insensitive to coffee may still have a delayed body clock from drinking coffee at night is an open question, Professor Wright says.
Advertisement
GREENFIELDBOYCE: He says people really need to think about how and when they’re using caffeine. He adds that a lifestyle with irregular sleeping habits and poor quality sleep is bad for the organism, because the circadian body will be out of sync with the one of the natural world.
