Suffer from 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 exposure to daylight is important for avoiding the winter blues. However, scientists have now found that exposure to bright daylight is actually vital throughout the year.
Without enough 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 diseases.
This phenomenon - “social jet lag” - 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 comes.
Bright light in the morning stimulates the production of chemicals such as adrenalin, cortisol and serotonin which help wake us up, fire our energy and make us feel mentally alert, says Daniel Adams, a US scientist and expert on light therapy.
“The production of these ‘waking’ hormones also help wash away the hormones that make us feel sleepy. Then, 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.”
That’s what should be happening. But, nowadays, we often get up in the dark and spend much of our time during the day inside in the relative gloom.
Then, as darkness falls, we turn on the lights. Before bed, we go into the bathroom - often the brightest room - 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 neuro-endocrinologist at the University of Surrey.
This limited 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 Munich University, believes many people are affected by it. “More than 50 percent 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.
“That is why so many people struggle to get up in the morning - 74 percent of people need an alarm clock to wake them - their body clock is behind the real time.
“They 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. “Our body 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.
“It also 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 US 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 Skene. “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.”
Only in the past 10 years have scientists such as Professor David Berson, a US neuroscientist, started to understand the role light and our eyes play in setting our body clock. His team recently discovered the role of a light-sensitive pigment in the eye called melanopsin. When it senses bright light it stimulates the production of nerve signals which send messages to the suprachiasmatic nucleus - the section of the brain known as the body clock. The brighter the light, the greater the intensity of the signals sent.
“Our body clock is a bit like a cheap digital clock, it isn’t perfect at keeping time and tends to drift,” he says. “It is exposure to light that helps correct these errors and keeps it to a normal pattern.” - Daily Mail