Lynne Peeples (Out 24 September: Bloomsbury Tonic (UK); Riverhead Books (US))
The little penguin (Eudyptula minor), a tiny, blue bird living off the coast of southern Australia, speed-wobbles from the ocean to its burrow home at the same time every day 鈥� just after sunset. Timing is crucial: too early and they miss the day鈥檚 final catch; too late and encroaching darkness makes them prey for orcas and feral cats.
Fortunately for those who come to watch, environmental cues like sunlight and phases of the moon let E. minor keep their internal clocks tethered to the 24-hour day, ensuring a great show and giving them the best chance of survival.
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Much like these penguins, we also have thousands of internal metronomes, orchestrating everything from sleep and metabolism to our ability to ward off disease. Our main pacemaker, in the brain鈥檚 hypothalamus, is linked to the 24-hour day via pathways from the retina, which respond to different types of light to synchronise biological rhythms. Unfortunately, modern life is causing these rhythms to fall out of sync.
Science journalist Lynne Peeples is here to make sure we realise that this is a big problem. In The Inner Clock: Living in sync with our circadian rhythms, she shows how our biological timers are thrown off by everything from work patterns to environmental pollution. This wreaks havoc on our mental and physical health, she says, and we are only just beginning to fully appreciate the consequences.
We join Peeples during her vacation in a decommissioned nuclear missile complex, where she shut herself off from natural light to see how her body reacted without external cues about the time. Most of us don鈥檛 need to go that far: spending too long in dim offices or staring at bright phones at night is enough to confuse our biology. A world of dark days and bright nights has sent circadian clocks straying from the sun, with consequences ranging from poor sleep and concentration to diabetes. It might even increase our risk of dementia. Circadian rhythms control the mopping up of proteins linked with Alzheimer鈥檚 disease 鈥� when they falter, so does the clean-up.
The Norwegian valley of Rjukan uses mirrors to reflect sunlight on residents otherwise living in shadow
. She cites the Norwegian valley of Rjukan, where computer-controlled mirrors sit atop a mountain wall flanking the town鈥檚 centre. The mirrors follow the sun, reflecting rays on residents who would otherwise live in shadow.
There are simpler ways of illuminating your life, of course. Take tunable LED lighting systems, which vary in intensity so indoor light can follow the variation of natural light. A football team might use dim yellow lights in the locker room after an evening game to help them unwind, for instance.
Even painting walls white, or moving a desk near a window, will provide extra rays. It is worth it 鈥� the gain in alertness and cognition from meeting even minimum standards of 250 lux at work is remarkable, says Peeples, on par with an hour or two more sleep.
Increased understanding of the importance of biological rhythms has led to exciting applications. There are hints at potential benefits from taking vaccines at certain times of day, feeding sick babies in tune with their internal clocks and even targeting cancer more effectively at night.
Other writers have illuminated the power of light and circadian rhythms on our health 鈥� Linda Geddes鈥檚 Chasing the Sun is a notable predecessor. But Peeples has new stories and surprises, not least in how many circadian disrupters 鈥� salt and bisphenol A (BPA), for example 鈥� have been discovered in recent years.
More on this would have been welcome, but readers need have no fear: you will still find plenty of practical tips here on how to sneak an extra 鈥渃ircadian snack鈥� into your lives, reset your chronicity and live in a healthier, more timely manner.
Helen Thomson is a writer based聽in聽London
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