Body clock: What makes you tick?
As leading scientists warn that society has become "supremely arrogant" by ignoring the importance of sleep and the body clock, scientists examine the profound impact our internal clocks have on our body.
The eight body clock phases:
Heart attacks more likely
Men have their testosterone peak
Be careful - this is the time of day your heart is most vulnerable. Blood vessels are stiffer and more rigid, the blood is thicker and stickier and your blood pressure is at its peak. It all adds up to the greatest risk of a heart attack you'll face today. Your body is kicking into gear as sleep hormone melatonin production stops. It is a poor time to exercise.
How does the body clock work?
Nearly every cell in every tissue in every organ has a daily rhythm and a clock controlling it. The suprachiasmatic nuclei (SCN) in the brain acts as the master clock and keeps the body working to the same time. It roughly follows a 24-hour pattern. Light is crucial. Special cells in the eye respond to light and keep the SCN in tune with the wider world. It also stops the sleep hormone melatonin being made during the day.
You're probably in work and it's time to get some of the heavy thinking done. The stress hormone cortisol reaches its natural peak giving our brains a boost of alertness. We tend to be most productive before lunch and tests show short-term memory is at its best. Stay busy, there's a big dip coming up.
Why work leaves us jet lagged?
Social jet lag is the difference between the time your body thinks it is and the time society says it is. Your body clock uses light to tell time, but society uses clocks. Getting up early before your body is ready leaves you tired and out of sorts. The more you sleep in at weekends, the more socially jet-lagged you are. The difference between weekday and weekend sleep can be the equivalent of flying from London to New York on a Friday night and flying back on a Monday morning.
Increased gastric activity
Post lunchtime dip in alertness
With a lunchtime belly full of food, there's a boost in gastric activity. But this soon adds to the 'biological siesta' as alertness dips and affects driving ability. There's a noticeable rise in the number of deaths on the roads from 14:00, particularly in older people. It's also a bad time to drink alcohol as it can make you more drowsy than at other times of the day.
Best lung & cardiovascular performance
Core body temperature rising to its peak
Go get a sweat on! Body temperature increases in the late afternoon like a natural warm-up, the heart and lungs work better and muscles are 6% stronger than at their lowest point in the day. Some people have even tried using this 'athletic sweetspot' to increase their chances of breaking sporting world records.
Is there a best time to take medication?
If your body changes through the day, then the effect drugs have might change too. The symptoms of rheumatoid arthritis wax and wane with the body clock and doctors think they can improve treatment by timing drugs. Heart disease is driven by artery-clogging cholesterol, which is mostly made in the liver at night. Taking statins in the evening makes them more effective. The whole body tries to run to the same internal time, but cancers do their own thing. Chemotherapy kills rapidly dividing cells, so researchers are trying to take advantage of cancer clocks by using chemotherapy when the cancer cells are dividing but cells in the rest of the body are not.
Poor time to eat a big meal
Liver handles alcohol better
Intuitive thinking is better
Ready for dinner and maybe a drink? Well you might not want to leave it too late. Emerging evidence suggests the body changes the way it handles food as it gets closer to night-time. Eating big meals in the evening could increase the risk of obesity and diabetes. The liver is more able to deal with alcohol if you fancy a tipple.
Melatonin production building
Core body temperature dropping
Bedtime is fast approaching and the pineal gland in the brain is churning out the hormone melatonin to help you nod off. Core body temperature is falling and the internal body clock is saying it's time to swap the sofa for the duvet. It'll happen first if you're a morning or 'lark' type person, before hitting the 'owls' a bit later.
Sleep hormone melatonin peaking
Minimum levels of attention and vigilance
Brain washes itself and consolidates memories
It is well and truly bedtime. Hormonal changes in the body say it is time to be asleep. The brain is washing away the waste toxins built up during a hard day's thinking and the bowels are shut down for the night. If you're still awake be careful, levels of attention are at their lowest, making industrial accidents a risk on night shifts.
Minimum core body temperature
Severe asthma attacks more common
Most natural births occur
It's the heart of the night and your body is still some way off waking up and getting you out of bed. Sleep hormone melatonin levels are still high, but glide down as dawn approaches. Your core body temperature is notably cooler than any other part of the day as energy is diverted elsewhere, such as skin repair.
Will shift work be the death of me?
According to the European Commission, approximately 18% of all employees aged 15-64 in the EU currently work shifts. This can mean greater working flexibility and even more time off, but there can be impacts on your health when you try to function outside of the normal rhythms of your body clock. Shift work is associated with an increased risk of cancer, obesity, type 2 diabetes, heart attack and stroke. Public health scientists have called for more research into how to protect the health of shift workers.
Personal body clock quiz:
During my research i found a quiz that analyses if you are a morning or evening person? This questionnaire helps you to work out if you are a lark or an owl, or whether you have a more balanced body clock.
Authors: James Gallagher, Rachael Buchanan and Victoria Gill
Produced by: Andreia Carqueija, Richard Bangay, Marcelo Zanni, Helene Sears and Dominic Bailey
With thanks to researchers at The University of Oxford, The University of Manchester, The University of Surrey, The University of Cambridge and Harvard Medical School.
