Jan Denneman, Chairman of the Board at Good Light Group (Master’s degree, Physics; Eindhoven University of Technology, says, “There’s hardly a living creature that willingly stays indoors, with a few exceptions.” We’re all familiar with the benefits of exercise, a balanced diet, and enough relaxation for good health. But did you know that light plays an equally crucial role? Those who maintain a healthy exposure to good light tend to sleep better, experience reduced stress, more energy and happiness.”

In winter, when daylight hours are shorter, how does this impact us as humans?
“At this time of year, we often feel more tired, down, and our circadian rhythms are frequently disrupted. Scientifically proven, people tend to be less happy during the winter compared to summer, simply because you get insufficient daylight.”

Why is daylight essential for a happier life?
“It’s how nature operates. Just as a compass aligns with the Earth’s magnetic field, humans are designed for daylight. All life on Earth – plants, animals, and even microbes in the sea – relies on daylight. With a few exceptions (like moles), no living creature voluntarily chooses to stay indoors. However, centuries ago, humans started spending more time indoors, which goes against our natural instincts and internal body clocks.”

How does our biological clock function?
“The biological clock, located in our brain, prepares our bodies for upcoming events, such as a good night’s sleep. Synchronization with real-time is crucial for a properly functioning biological clock. If you naturally wake at 7 am and sleep at 11 pm, your biological clock is likely in good shape. But, if you consistently wake up tired and rely on an alarm clock, your biological clock may be disrupted.

Scientific studies indicate that you can only synchronize your biological clock with light. Apart from rods and cones, which enable vision, our eyes also contain spheres linked to the biological clock and mood regulation. These cells require more light than those responsible for vision. Therefore, I always carry a light meter to ensure I’m exposed to sufficient light to stimulate these cells.”

How do we know if we’re receiving sufficient light, and if these spheres are doing their job?
“According to research, during daylight hours (between 7 am and 6 pm), you should receive at least 250 lux of natural light or 400 lux of artificial light through your eyes. Convenient apps like Light Meter for the iPhone can measure illuminance. Outdoors, you’ll naturally receive 250 lux or more when the sun is up, but indoors, unless you’re near a window, you’ll need to adjust lighting. However, in the evening, aim for much lower light levels, ideally less than 10 lux, to prepare your body for sleep.”

What are some practical tips for increasing daylight exposure during dark days?
“Morning light is most effective, so go outside when the sun rises. Even on dark, rainy days, outdoor light is significantly stronger than indoor light and adequate for our eye spheres. Staying indoors? Ensure sufficient artificial lighting.

Secondly, opt for a workspace with a window view, as you can benefit from daylight without stepping outside. Also, take regular breaks to gaze out the window for at least 20 seconds every 20 minutes; it relaxes your eyes and provides light exposure. Do you struggle to wake without an alarm clock? Consider using a light-based alarm clock. This allows your body to awaken naturally from deep sleep without being startled of the jarring sound of a traditional alarm.”

And thirdly, install extra light during the day if you are not able to be close to a window with natural daylight. You should at least get a light intensity of 400 lux in your eyes during the whole day, and less than 10 in the evening.

Original Dutch text by: Djaydee Kraus
Source of information: https://www.goodlightgroup.org/post/humans-need-sufficient-daylight-it-s-inherent-to-our-nature
Watch the masterclass (in Dutch): https://youtu.be/B8nRvbSQqrs?si=y9GmnviZR-5xQ6Tq