Drinking coffee late in the evening does more than just keep you awake at night, research has shown. |
Evidence shows that it can go as far as resetting the internal body
clock which regulates a number of biological functions and genes that work
around a natural day/night cycle.
To put that into context, scientists say that drinking the equivalent
of a double espresso three hours before bedtime can turn the body clock back
nearly an hour. Essentially, it makes your body think it is in a different
time-zone.
Caffeine resets the clock by delaying a rise in the level of melatonin,
the body’s chief sleep hormone, which fluctuates in levels to 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.
Effects of coffee can affect
whole sleep patterns.
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.
“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, it gives greater insight into how we can influence our
natural 24 hour cycle, for better or for worse.”
All body clock patterns – right down to the level of individual cells –
also known as ‘circadian rhythms’, are governed by a “master clock” in the
brain that controls the release of melatonin and which 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 sleep time delayed the expected melatonin surge by 40
minutes. Caffeine and bright light combined extended the delay to 105 minutes.
To further investigate what was happening, the UK scientists led by Dr
O’Neill added caffeine to human cells in the laboratory.
They found that at the cellular level, caffeine can turn the clock back
directly by activating a receptor protein “switch” found in all cells. Reducing
levels of the switch protein on cell surfaces minimised the caffeine-induced
body clock delay.
Professor Kenneth Wright, from the University of Colorado’s Department
of Integrative Physiology, said: “This is the first study to show that
caffeine, the most widely used psychoactive drug in the world, has an influence
on the human circadian clock.
“It also provides new and exciting insights into the effects of
caffeine on human physiology.”
The results may help explain why caffeine-drinking “night owls” go to
bed later and wake up later and may have implications for treating some
circadian sleep-wake disorders, he added.
Source:
The above findings were recently reported in the journal Science Translational Medicine.
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