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In the cold light of day

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Sunlight is good for our health and wellbeing even during winter. It’s important that we harness its benefits.


Sunlight is vital for many reasons – sleep, concentration, mood and wellbeing. Even this doesn’t cover all its benefits, as experts say we still don’t know the whole story about sunlight’s power. So, are we dangerously in the dark about the benefits of light? And how can we bring more of it into our working lives?

Sleep and mood

One of the most well-known side effects of using screens at night is disturbed sleep. Yet, possibly less is known of the positive correlation to this – that natural light during the day can also improve sleep, productivity and mood.

Daylight helps stimulate production of hormones that help us sleep at night. Photograph: iStock/David Fairclough

There is no life without light, but as humans we are moving further away from daylight. The average person in the UK today spends 22 hours indoors – roughly 90 per cent of their day, according to a recent Opinium study. And, as jobs become more automated and computer-focused, we become even more severed from our natural environments.

Unsurprisingly, this is taking its toll on people. Nearly a third of UK adults say their sleep has worsened in the past year, according to the Mental Health Foundation’s January survey. Studies show this increases the risk of disorders including high blood pressure, cardiovascular disease, diabetes, depression and obesity. 

The science of sunlight

The hormones we need for sleep derive from sunlight – and this process begins as soon as we wake and the rays, however weak and wintery, penetrate the subset of cells, just behind the eye, sending messages to our brain and body clock, setting the cogs in motion. In the words of Linda Geddes, author of Chasing the Sun: The New Science of Sunlight and How it Shapes Our Bodies and Minds, sunlight speaks to “a tiny patch of brain tissue which functions as the body’s masterclock, tweaking its timing.”

Daylight helps stimulate production of hormones that help us sleep at night, melatonin being the core sleep regulation hormone, explains Miranda Loh, director of growth, scientific engagement and innovation at the Institute of Occupational Medicine (IOM). “Sunlight exposure plays a role in stimulating serotonin, which boosts mood but is also a precursor to melatonin as well. Melatonin is a hormone that promotes sleep.”

Our biology is set up to work in tandem with Earth’s 24-hour cycle of light and dark: “Your Circadian rhythm is based around light.”

Studies have shown this to be true. In May 2020, the International Journal of Environmental Research and Public Health (IJERPH) published its research based on a cohort of 30 office workers. After working by light-filled windows, the cohort slept 37 min longer and scored a massive 42 per cent higher on cognitive performance tests compared to a week they spent in an identically shaped, but dingy office with blinds.

But there are many more benefits to sunlight too – not just sleep and productivity. Also, it can help manage mental health conditions like depression and anxiety. For example, sunlight exposure in patient rooms has been proven to aid recovery from depression (Beauchemin and Hays, 1996, Canellas et al., 2016). For healthy individuals as well, a 30-minute exposure to daylight has been found to improve mood (Kaida et al., 2007). 750 individuals were asked to report on their feelings of happiness and sadness in response to natural lighting conditions in home working environments, for a study published in 2022 in Building & Environment Journal. It found that settings with the most daylight entering the home led to the greatest impacts on mood states.

The heart of the matter

Yet, despite the long list of benefits, scientists are still discovering that we don’t know everything about sunlight’s power. There’s evidence, for example, (see the study Dying in the dark, Journal of the Royal Society of Medicine) that heart attack victims are less likely to die if they are in sunlit wards.

Professor of Medical Dermatology at the University of Edinburgh, Richard Weller, has been studying the impact of sunlight on heart health for several years. A 2013 study he conducted on the arms of individuals exposed to ultraviolet (UVA) lamps showed how the light activated the skin’s stores of nitric oxide (NO). NO is involved in the regulation of blood pressure, which reduces the risk of heart attack or stroke.

A walk outside is good for wellbeing. Photograph: iStock/SolStock

In his TED talk Could the sun be good for your heart? Professor Weller explores how this study, which demonstrated how sunlight can bring blood pressure down, could be evidence “enough to shift the rates of heart disease in a whole population.” More research is due out in April when the National Institute for Health and Care Research will publish its review on the data around sunlight’s health benefits.

Vitamin D – hogging the limelight? 

Today, Professor Weller worries that too much attention has been given to the sun’s role in production of Vitamin D. “The fixation on vitamin D has obscured the benefits of sunshine and Vitamin D’s benefits are hugely overstated,” he shares with me on email. “Probably only a few benefits of sunshine are caused by vitamin D. It stops rickets and prevents progression of some cancers.” He adds that studies on vitamin D supplements have failed to prove that they lead to “good health”: “It is a $3 billion dollar industry worldwide, but as a health supplement rather than medicine there is little regulation about claims.”

Working by light-filled windows has been linked to improved cognitive performance. Photograph: iStock/Zorica Nastasic

For Professor Weller, vitamin D is more helpful as a ‘biomarker’ of our general exposure to daylight and sunshine and the health benefits we accrue that way. “High vitamin D levels are a marker for sunlight exposure and sunlight exposure is good for [combating] heart disease. Getting outside is good, taking exercise.”

Yet we are told that taking a vitamin D pill will do the trick for our health in winter. Could this mean we are missing out on the real thing? That’s what Geddes certainly found when she dedicated a week to getting outdoors as much as possible. She cycled to work, ate her lunch outside and moved her desk to by a window. “It changed me,” she says on her website. Mainly it was about mood and productivity – not only did she feel sleepier at night but more alert and cheerful in the mornings. But this may be just a fraction of what’s going on in the body.

Risk communications – a balance?

We’re discussing winter light and its benefits here, but it’s important not to overlook the sun’s dangers for workers in the UK and around the world. Latest figures from the World Health Organization (WHO) and International Labour Organization reveal that nearly one in three deaths from non-melanoma skin cancer are caused by working in the sun. 1.6 billion people of working age were exposed to solar ultraviolet (UV) radiation while working outside in 2019, equivalent to 28 per cent of the world’s working population.

Sun safe behaviours, while advanced in Australia where skin cancer rates have come down on the back of campaigns like slip slop slap!, are not yet ingrained in the UK, says Loh: “In a climate like the UK, most people won’t think of sunlight as an occupational risk.”

The IOM together with Heriot-Watt University found evidence for this in their 2019 intervention, which sought to influence construction workers to cover up or wear sunscreen via text messages which carried advice and support.

Loh reflects on the study: “We found an indication that people knew the sun was bad for you but weren’t actively doing anything about it. People felt positive attitudes around having a tan – that kind of attitude would lead people to be less proactive about sun protection.”

Even so, surely there’s a balance to be had? In their July 2020 paper, Insufficient Sun Exposure Has Become a Real Public Health Problem, health academics write: “Current public health advice on sun exposure ought to be reconsidered to communicate a better balance of the benefits and harms of sunlight, particularly at higher latitudes… Most research to date has focused on adverse effects, with vitamin D synthesis being seen as the only established benefit.”

‘Whatever the weather’

In winter, in the UK, given that we are located at high latitude (far from the equator) and so receive less sunlight, there’s an opportunity to promote more the benefits of using what light we do have. “If you’re going to promote ‘take a walk for wellbeing’ for example, you could add in the benefits of getting sunlight exposure as well as fresh air and exercise,” says Loh. “In general, I think it’s about taking time away from your tasks and a shift in your environment which is good for the mental health side of things.”

And however gloomy those days are, experts say it’s still worth dragging yourself out the door to get some light. “In winter, even on an overcast day it’s at least 25 times brighter outside,” says Geddes. “We need to get out there and embrace that light, whatever the weather and the season.” It’s important to stay connected to daylight and we must get as much of it as we can. Or, as Professor Weller says: “My advice is to get outside. Sunshine is free!”

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