The evidence suggests that the effects of caffeine go much further than simply making it harder to sleep.
Scientists discovered that drinking the equivalent of a double espresso three hours before bed-time can turn the body clock back nearly an hour.
Caffeine resets the clock by delaying a rise in the level of melatonin, the body's chief sleep hormone. Coffee drunk late in the evening resets the internal body clock which regulates a host of biological functions and genes according to a natural day/night cycle, research has shown.
Coffee drunk late in the evening resets the internal body clock which regulates a host of biological functions and genes according to a natural day/night cycle, research has shown.
Fluctuating levels of melatonin help determine the natural time to go to sleep and wake up. Two teams of British and US scientists carried out a study of volunteers and observed what happened to individual cells exposed to caffeine. Joint lead researcher Dr John O'Neill, from the Medical Research Council Laboratory of Molecular Biology in London said: "The effect of caffeine on sleep and wakefulness has been long established, but its impact on the underlying body clock has remained unknown. "These findings could have important implications for people with circadian sleep disorders, where their normal 24 hour body clock doesn't work properly, or even help with getting over jet lag.
SEE ALSO:"Our findings also provide a more complete explanation for why it's harder for some people to sleep if they've had a coffee in the evening - because their internal clockwork thinks that they're an hour further west. "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." Body clock patterns, also known as circadian rhythms, are governed by a "master clock" in the brain that governs the release of melatonin. The mechanism, which synchronises clocks that exist throughout the body right down to the level of individual cells, is itself governed by exposure to light entering the eye. Disruption of the body clock, for instance by working shifts or jet lag, is known to increase the risk of various cancers, heart disease, Type 2 diabetes and neurodegenerative disorders such as Alzheimer's. In the US study conducted at the University of Colorado, researchers tested the saliva of five volunteers to look for signs of rising melatonin. They found that stimulation by the caffeine equivalent of a double espresso coffee three hours before it was time to sleep delayed the expected melatonin surge by 40 minutes.
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