When it comes to health, we often talk at length about what we eat and drink, but perhaps the most overlooked nutrient of all is natural light. In her new book, How to Age, Liz Earle describes light as “one of the most powerful pro-ageing tools we have”, highlighting its influence on everything from our mood and metabolism to sleep and cognitive health.
And it isn’t a radically new concept. Our ancestors lived by it for millennia, rising with the sun and resting as it set. “From an evolutionary perspective, our bodies were designed to follow the sun,” says Liz. Modern life, however, has made living in sync with our natural rhythms increasingly difficult.
“We think of light as something that helps us see, but it also helps the body know,” Liz adds. Morning sunlight, for example, reaches specialised receptors in the eye that communicate directly with the brain’s master clock, helping to regulate hormones, energy levels and our sleep-wake cycle. Yet many of us treat light as incidental – something that happens to reach us when we’re outside, rather than something we actively seek out.
Here, we explore how the quality of light shifts throughout the day, and how tuning into those changes can support energy, hormones and sleep.
How to hack daylight for better health
Dawn: First light
The early bird might catch the worm, but getting outside at dawn is one of the best things we can do for our health too. Most of us have heard of the 5am club, but those eager early risers may actually be onto something.
Dawn light is rich in blue and red wavelengths, with the sun sitting low on the horizon. It’s this specific quality of light that triggers the body’s photoreceptors to reset our circadian rhythm.
Dawn light also triggers a precise cortisol awakening response. This is a natural hormonal surge that primes alertness, metabolism and immune function for the day ahead.
“Morning sunlight tells the body it’s daytime,” says Liz. “It lowers melatonin (our sleep hormone) and raises cortisol in a healthy, awakening way, setting off a cascade of biological activity that boosts mood, metabolism and energy.
“That’s why stepping outside for just 10 minutes early in the day can make such a dramatic difference to how energised, focused and balanced we feel, and how well we sleep that night.”
Cognitive strategist, Natalie Mackenzie, agrees and recommends getting outside within 30 to 60 minutes of waking, even on a cloudy day. Dawn light initiates the release of serotonin, and with it, a timer of sorts: “Roughly 14 to 16 hours later, the brain will begin converting that serotonin to melatonin and the wind-down toward sleep will begin,” she says.
“That first hit of cool air and early daylight isn’t just invigorating, it’s biological clockwork,” adds seasonal nutritionist, Fiona Berry.
If we miss this window – as so many of us do when we move straight from bedroom to screen – that finely tuned cascade can be disrupted before the day has even begun.
Early morning
For those of us in need of a little more shut-eye, all is not lost. Around 60 to 90 minutes after sunrise still carries plenty of benefits. A morning walk, or simply taking a cup of tea outside, is a gentle way to reap the rewards of early morning light.
Natalie recommends eating breakfast near a window or outside where possible. “Combining food, light and movement in the morning reinforces the circadian signal and supports the hormonal rhythm of the day,” she explains.
But it’s not just our internal rhythms that benefit. This is also an ideal window for skin to absorb softer light directly.
“It’s precisely this window when UVB rays begin stimulating vitamin D synthesis,” says Fiona. “This is a nutrient critical not just for immunity and bone density, but for skin cell turnover and barrier repair.” She advises leaving SPF off for 15 to 20 minutes before UV intensity builds, too.
Avoiding sunglasses during this window can also be key. “Sunglasses filter out the very wavelengths the photoreceptors most need for circadian signalling,” Natalie explains. Save them instead for midday, when the light is more intense and UV protection is genuinely needed.
Midday: The vitamin D window
Midday light is bright, overhead and full-spectrum – the most intense light of the day. And while we’re all for skin safety, when that midday sun hits, you don’t have to immediately reach for the sun cream. Getting five to 10 minutes of unprotected sunlight – adjusted for your skin type – can give your body a meaningful boost of vitamin D.
Vitamin D is synthesised in the skin through UVB exposure and acts more like a hormone than a vitamin in the body. “Vitamin D receptors are found throughout the brain, including in regions associated with mood, memory and cognitive function,” Natalie says.
“By enhancing the production of dopamine and serotonin, vitamin D supports emotional balance, mental clarity and overall resilience,” says Liz. “It’s one of the nutrients I’ve long recommended for navigating midlife with more energy and calm. The best way to optimise vitamin D is through safe, consistent sun exposure, especially around midday when UVB levels are strongest (but avoid burning).”
The light at this time of day can also help with getting our most demanding work done. “Midday’s intense blue-white light peaks cortisol and sharpens cognitive focus,” says Fiona.
Natalie agrees. She says that even brief exposure to bright natural light at this point in the day has been shown to improve afternoon alertness and reduce the post-lunch energy dip. “If there is a time to step away from the desk and get outside, midday is it.”
This is especially important, she notes, for women in midlife, when hormonal changes are already placing demands on the brain’s regulatory systems.
Evening
By evening, those amber and rose tones of a setting sun are more than just a pretty way to end the day. Think of them as a neurological dimmer switch.
“As the day winds down, so should our light exposure,” says Liz. “In the evening, when the sun sets and things get dimmer, the absence of blue light signals the brain to ramp up melatonin, preparing us for rest and renewal.”
Natalie agrees, and says this is the moment to start reducing blue light from screens. “Keeping light sources bright and blue into the evening delays melatonin onset,” she explains. “It pushes back sleep and degrades its quality, particularly the deep, slow-wave sleep that’s most restorative for the brain.”
Just as eating with the seasons can enhance our wellbeing, so too can living seasonally throughout the day: morning light to reset the internal clock, midday light for vitamin D and alertness, and dimmer evening light to begin the neurological wind-down.
“The extraordinary thing is how little it takes to reconnect with these rhythms,” says Fiona. “10 minutes at dawn, a lunchtime walk, screens down as the light fades.”
As for what we can do at home, dim overhead lights and switch to lamps with warm bulbs. Put screens on night mode two hours before bed. A blackout curtain or a good sleep mask is also worth considering. This helps to avoid early morning light disruptions before you’re ready to wake.
A final note
So, before you go running out into the sunshine, Natalie reminds us to take the seasonal context seriously. “In the UK, UVB light is insufficient for vitamin D synthesis between October and March, regardless of time spent outside,” she explains. This means for women in midlife already navigating hormonal changes that affect brain chemistry and mood, a vitamin D supplement through those months is a simple, well-evidenced step worth discussing with your GP.
