In the past, we organised our daily routines according to the sun. Sunlight was our main source of light and energy, with our ancestors working outside from sunrise to sunset. Dimly lit nights were spent with candles and around the fireplace, followed by going to sleep in darkness. Nowadays, many of us live in big cities, work inside big buildings and use artificial light and digital devices all day and night. Our social clock is out of sync with our solar clock and body clock. With our modern lifestyles, we have become more removed from the natural world. This has happened in the last 140 years, beginning with the development of the light bulb in 1879 and more recently with the widespread usage of artificial light sources and artificially lit screens.
There are many ways sunlight impacts our physical and mental health, with the most important being vitamin D synthesis and the regulation of our body clock. Every cell, tissue, organ and organ system in every organism has an internal biological clock synchronised with the day/night cycle of the sun. This hard-wired 24-hour clock is called the circadian rhythm – we are all governed by it. It is the major regulator for our health: it helps our sleep/wake cycle, mitochondrial function, gene expression, immune and inflammatory responses, hormone production, cardiovascular function and brain wave activity, just to name a few!
Until more recently, we only knew about two types of photoreceptors, the cells in the retina that respond to light. We thought retinal cone and rod photoreceptors were entirely responsible for light sensitivity. A third photoreceptor cell in the eye, called intrinsically photosensitive retinal ganglion cells (ipRGCs), was discovered only recently during the 1990s. These are not involved in seeing but play a crucial role in regulating our circadian rhythm.
The ipRGCs transmit information about light received to your master biological clock, the suprachiasmatic nucleus in the brain (SCN). The SCN processes this information and relays it to the pineal gland in the brain. Research has shown how this gland impacts many physiological processes, producing the sleep hormone and potent antioxidant melatonin, whose primary role is to regulate the body’s circadian rhythm.
Depending on the time of day we are exposed to it, blue light can have both positive and negative effects. When we are exposed to blue light in sunlight during the morning, it helps boost concentration, learning, memory, reaction times and boosts our mood. In the evening, the levels of blue light drop as the sun sets. Melatonin is then produced, helping us fall asleep. Melatonin levels typically stay elevated for about 12 hours and as the sun rises, your pineal gland reduces its production and the levels in your blood decrease.
Artificial light from lighting and digital devices does not resemble sunlight. It never changes during the day and it differs in its combination of frequencies, with up to 35 percent of it being blue light, much more than in sunlight.
We spend most of our waking hours on digital devices, including computers, smartphones, tablets, e-readers and watching television. We use our smartphones every day, sometimes every hour. Work, browsing the internet, apps, banking, entertainment and social media all add up to unnaturally high levels of blue light exposure. Sometimes we are on multiple devices at the same time: watching television with a phone next to us and having an iPad within reach.
Out of all the wavelengths, blue light has the most impact on our body clock and thus our health – it is most disruptive at night. Bright blue-rich light at night tricks our brain into believing it’s still daytime, so falling asleep can be more difficult and sleep quality can be disrupted.
Incandescent bulbs most closely simulate daylight, but are being phased out and replaced with more durable and energy-efficient options. Newer artificial light sources, including fluorescent and LED lights, emit a lot more blue light.
Prolonged and close-range exposure to blue light, especially in the evening and before bedtime, can have adverse effects on the body clock. If it is advanced (ahead of time) or delayed (running behind) compared to expected timing based on cues like sunlight, our homoeostasis is disrupted. This can cause sleep issues, impaired functioning and other negative health impacts.
Humans have not biologically adapted to this change in lighting. I believe the epidemic of chronic illnesses is due not only to our modern diet and stressors, but also to the lack of appropriate sunlight exposure during the day, excessive blue and artificial light exposure in the evening and not sleeping in darkness at night.
Light and its absence, that is, darkness, are the most important factors that can affect our sleep and our body’s processes. In the evening, we need to avoid blue light so melatonin is not suppressed.
Green light, next to blue on the light spectrum, also exerts an impact, although a much weaker one.
Conditions related to body clock dysfunction include:
* Metabolic diseases like diabetes and obesity;
* Cardiovascular problems like high blood pressure and heart disease;
* Hormonal issues;
* Immune system issues;
* Mental health problems like depression and SAD (Seasonal Affective Disorder);
* Bone issues like osteoporosis;
* Degenerative brain conditions like Alzheimer’s disease;
* Skin damage;
* Eye issues and disease;
Research has found another issue with blue light – at high levels of illumination, this high-energy wavelength can be directly toxic to cellular structures. Artificial light can affect our eyesight, causing blur, eye fatigue, dry eyes and headaches. As blue light can penetrate further back in the eye, it may also contribute to eye diseases like cataracts and retinal damage like macular degeneration through oxidation.
We have learnt to shield our skin from the sun’s UV radiation, as we have been told it harms the skin and hastens the ageing process. However, scientists concur that excessive blue and green light can also harm our skin. Exposing our skin to blue light can directly damage skin cells through oxidation and inflammation, accelerate the ageing of the skin, increase wrinkles, affect our fat cells and diabetes.
We all need protection from artificial blue light exposure, but some of us are more vulnerable to its negative effects:
* Children and teenagers;
* Night workers and shift workers – at higher risk for obesity, heart disease, diabetes, breast, prostate, and colon cancer;
* Frequent travellers and airline staff – moving through different time zones;
* The elderly – poorer circadian signalling of light;
* Location – living in higher latitudes means less sun exposure;
* Those with health issues; poorer lifestyle choices; taking certain medications.
To mitigate the adverse effects of blue light exposure on sleep and overall wellbeing, we have many strategies.
My suggestions include:
* Get direct sunlight exposure through the eyes and onto the skin early in the morning and throughout the day—take your lunch break outside!
* Minimise time spent on digital devices and have visual breaks (every 15 minutes) and physical breaks (every hour at least!) away from ALL screens; sit near open windows to balance the light you are exposed to.
* Use the blue light filter/night mode/eye shield feature on all devices all day to reduce blue light exposure and minimise the brightness of your screens. Even Apple understands the importance of minimising blue light and offers these options on its devices.
* Wear blue light-blocking glasses or get this filter on your prescription glasses for indoor use only. Yellow, amber or red lenses in glasses or fit-overs removes more blue light and are suitable for night use.
* Switch off all digital devices at night at least two hours before bedtime.
* Dim lights at night and keep lights lower off the ground.
* Replace lighting with blue-light-free light bulbs (yellow, amber or red). Use lights closer to the floor, for example, lamps rather than ceiling lights.
* Take away digital devices from children’s bedrooms.
* When you feel sleepy, go to bed. Listen to your body! Try to get to bed before nine or ten at night to maximise melatonin production
* Sleep in complete darkness with blockout curtains and a sleep mask if you can’t control the light environment.
* Consume a diet high in colourful vegetables, fruit and green leafy vegetables. Phytopigments like carotenoids in our diet, for example, lutein and zeaxanthin, can reduce oxidative damage from blue light.
Although the lighting industry has established standards for protecting consumers from extremely bright light and UV radiation, there are no current standards addressing the blue light hazard. The majority of us don’t realise how significantly the lack of adequate sunlight exposure at the right time and our artificially-lit environments at work, home and school during the day and night have an impact on our body clock and consequently, our physical and mental health.
The prolific use of digital devices is so ingrained in our modern lives that it is contributing to a cascade of ill health. Every day you have a chance to rectify and improve this – it’s crucial to get only the right light at the right time for optimal wellbeing!
Dr Jenny Livanos is doing a special 2-session series in our upcoming webinar series, the first will be Natural Eye Exercises for Better Vision and the second night will cover Nutrition for Healthy Eyes.