We long to believe that we can be creatures of the day and night, that we can defy the dark to enjoy 24/7 lives defined by long working hours, minimal sleep and, if technology adverts are to be believed, going jogging in the middle of the night.
In fact, insists University of Oxford neuroscientist Russell Foster in Life Timewe are “not able to do what we want at whatever time we choose. Our biology is governed by a 24-hour biological clock that advises us when it is the best time to eat, sleep, think and undertake a myriad of other essential tasks.”
Pitched somewhere between science book and lifestyle manual, this is a comprehensive manifesto for living in harmony with our body clocks, penned by someone who has devoted his career to studying them. Chasing perfect synchronicity not only increases happiness and mental sharpness, he argues, but potentially reduces the risk of diseases such as obesity and diabetes.
Foster made his name in the 1990s with the sensational discovery that the eye contains light-sensitive cells that are not involved in vision. Instead, these cells are key to regulating circadian rhythms (circadian refers to a 24-hour cycle), enabling the body to detect via light levels whether it is night or day. Light signals are sent to the “master clock”, housed in an area of the brain called the suprachiasmatic nuclei, which then synchronizes with the external environment.
That process, he writes, sets the schedule for our internal workings: “For our bodies to function properly we need the correct materials in the right place, in the right amount, at the right time of day.” This involves thousands of genes being switched on and off in a specific order. “Proteins, enzymes, fats, carbohydrates, hormones and other compounds have to be absorbed, broken down, metabolized and produced at a precise time for growth, reproduction, metabolism, movement, memory formation, defense and tissue repair.”
Sleep, of course, is an essential component of that schedule. During slumber, our bodies fix themselves, remove toxins, process ideas and lay down memories. Centuries of research, however, have failed to fully crack its mysteries, such as why we spend 36 per cent of our lives asleep. There is not even a widely accepted definition of what shuteye is; Foster describes it, somewhat unsatisfactorily, as a period of physical inactivity that allows essential biological activities to take place.
But an inexact understanding does not mean we cannot sleep better and smarter, and this is the strength of Life Time. While the chapters, covering such topics as the dangers of shift work and the best time to eat, take us deep into the scientific research, acronyms and all, they are capped by simple, friendly Q&A sections covering questions to which we all want quick up -to-date answers.
Does melatonin work for jet lag? It does for some, to a moderate extent, but not for others. Foster avoids it, preferring to use light exposure to reset his body clock according to whether he is traveling east or west across time zones.
Does a disturbed sleep pattern — known as SCRD, or sleep and circadian rhythm disruption — increase the risk of Covid infection? Emerging research suggests night-shift workers with SCRD show higher rates of infection and hospitalization, and given that the immune system is subject to circadian regulation, the link requires investigation.
Parents of night-owl teens and older readers fed up of night-time visits to the bathroom will appreciate the insight on how sleep patterns change with age. There is also a helpful questionnaire to pinpoint your “chronotype”, or whether you are a morning or evening person.
But the genial consumer advice, sometime laced with “dad humour”, comes with a serious message for policymakers: “The fact that society is not embracing the science of circadian rhythms represents an immense squandering of resources, and a major missed opportunity to improve health at every level.”
Life Time: The New Science of the Body Clock, and How It Can Revolutionize Your Sleep and Health by Russell Foster, Penguin Life, £16.99, 480 pages
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