Scientists say, your nightly cup of
coffee may be keeping you awake for more reasons than you


 Research by
Science Translation Medicine
that caffeine was more than just a stimulant and actually slowed
down the body's internal clock. 


 In the study a double espresso three hours
before bedtime delayed the production of the sleep hormone
melatonin by about 40 minutes, making getting to sleep


 One of the researchers included Dr John O'Neill
from the Medical Research Council's Laboratory of Molecular Biology
in Cambridge told the BBC News website: "If you're tired and having
a coffee at night to stay awake, then that is a bad idea, you'll
find it harder to got to sleep and get enough sleep."


 As part of O'Neill's study, he grey cells in a
dish and exposed them to caffeine to work out how it changed their
ability to keep time. It showed the drug was able to alter the
chemical clocks ticking away in every cell of the human


 In an alternative study in the US, five people
at the University of Colorado Boulder were locked in a sleep lab
for 50 days, spending most of their time in very dim light, as
light exposure is the main way in which we control our body


 The scientists discovered that an evening dose
of caffeine slowed the body clock by 40 minutes - having a similar
effect to three hours of bright light at bedtime.


 Our sleep expert Dr Nerina advises to minimise
your caffeine intake by drinking more water, herbal teas, and
dilute fruit juices. She also says alcohol can impair deep sleep
quality so you are likely to wake up feeling tired and fuzzy-headed
if you have over indulged the night before.


 Want more expert sleep opinions? Check out our
very own Dr Nerina's sleep toolkit.