daytime tiredness? Poor concentration? Feel you’ve lost your
‘get up and go’? If you answered yes to any of these questions,
then lack of daylight could be to blame.
We all know
that, at this time of year, exposure to daylight is important for
avoiding the winter blues.
have now found that exposure to bright daylight is actually vital
throughout the year.
light – and, at the right time of the day – our body clock isn’t
set properly. It then races ahead – or occasionally lags behind – the actual time.
As a result
we feel tired at inappropriate times of the day, suffer from poor
concentration and mood swings, and need stimulants such as coffee
to keep us going. We’re also more prone to put on weight and
develop certain diseases.
This phenomenon – ‘social jet lag’, as it’s known – occurs because
our modern lifestyles conflict with the way we evolved.
Our body clocks
are based on early man’s habits of rising with the dawn and
going to sleep as darkness came.
in the morning stimulates the production of chemicals such as adrenaline,
cortisol and serotonin which help wake us up, fire our energy and
makes us feel mentally alert, explains Daniel Adams, a U.S. scientist
and expert on light therapy.
of these “waking” hormones also help wash away the hormones
that make us feel sleepy.
in the evening, as the light fades, the body clock sends signals
to the pineal gland to produce hormones such as melatonin and adenosine
which help induce sleepiness.
what should be happening. But these days we often get up in the
dark then spend much of our time during the day inside in the relative
‘Then, as darkness
falls, we turn on the lights. Before bed we go into the bathroom – often the brightest room in the house – to have a bath or clean
our teeth. This has the equivalent effect on the body of a mug of
coffee, waking us up,’ says Professor Debra Skene, a neuroendocrinologist
at the University of Surrey.
exposure to natural daylight – and too much light at the wrong time
of day – upsets the body clock. The man who coined the term ‘social
jet lag’, Professor Till Roenneberg, of the University of Munich,
believes huge numbers of people are affected by it.
More than 50
per cent of us suffer from a social jet leg of more than two hours,
which means that our body clock’s time and the social time
are two hours apart.
is why so many people struggle to get up in the morning – 74 per
cent of people need an alarm clock to wake them – their body clock
is behind the real time.
are trying to get to sleep and wake up at a time that is not biologically
right for them.’
He adds that
tiredness is not the only problem.
clock sets all our biological features such as our metabolism and
kidney function, too. If your internal body clock is not in synch
with real time, it increases the risk of being addicted to alcohol
or cigarettes – as you tend to use alcohol to calm down at night
and cigarettes as a stimulant during the day to stay alert.
increases the risk of being overweight, because social jet lag makes
us do things at the wrong body clock time, such as eating.’
It might also
raise your risk of diseases such as cancer. One U.S. study, in 2005,
found that having lower than normal levels of the sleep-inducing
melatonin hormone encourages the growth of tumours.
So why doesn’t
artificial light during the day kick-start the body clock? Because
it is not intense enough, says Professor Skene.
of light is measured in lux; even when it’s cloudy, natural
daylight is around 10,000 lux, but a well-lit office will be only
around 500. Laboratory studies have found that the brilliant blue
light you get with the white sunlight against a blue sky is the
most effective at helping to make us alert – and ultimately to sleep.’