It’s no secret that light impacts our wellbeing. Watching the sunset can make us sleepy; waking in a bright room can give us energy. It seems that light works with—and, sometimes, against—the biological processes in the body. “Our circadian rhythm, or internal clock, ensures that all the cells in our body adapt to environmental conditions throughout the day,” explains Henrik Oster, Professor at the Endowed Lichtenberg Chair of Neurobiology.
How light influences our daily routines
Ideally, our mornings begin with bright light for energy, and our evenings end with dark or indirect lighting to promote good sleep. “The sleep-wake rhythm, as well as hormones such as cortisol and melatonin, are strongly regulated by circadian rhythms,” says Oster. “There are times of day when we sometimes have more and sometimes less of them.”
This is important for the body to function. The internal clock is synchronized with the day to night rhythm via light; Only when the circadian rhythm is intact do we feel healthy. “Light also has an influence on certain neurotransmitters that are linked to our well-being,” says Oster. “Dopamine and serotonin play a role here; Light also helps to stabilize our inner rhythm.” When everything is in sync, we are more alert, more focused, and more efficient during the day.
Why a lack of light can trigger depression
In winter, however, these processes often get out of sync. “If you have a very robust inner system, you can handle it well, but someone who is more sensitive will cross the threshold at some point where the system is so disturbed that seasonal depression can occur,” says Oster. According to current figures, around three percent of the American population (about 10 million people) suffers from winter depression.
“Blue light has the most influence on our internal clocks,” explains chronobiologist Martha Merrow. “This means that warm light with a low blue component has less of an effect on
the body, while cool white light—which has a higher blue light component—is more likely to imitate daylight and can therefore keep us awake.”
To that end, she has this important advice: “It should be as dark as possible at night—this means not only no TV, but also no light from street lamps outside your bedroom window. This will give your body a clear signal to sleep.”
The best indoor light for your well-being
Lighting researcher Oliver Stefani knows what this should look like indoors. “On mornings, rooms should be illuminated over a large area: bright, rather cool white,” he says, noting that, at the same time, the spectrum should not be too artificial. This means that the color rendering under a light source should be as natural as possible compared to daylight. “Because we are so sensitive to light in the morning, we can use bright and cold light while brushing our teeth or drinking coffee,” he explains.
To that end, it’s also a good idea to use an alarm clock with a graduating light. According to studies, a slow progression, starting with dimmed light, has a positive effect on well-being. “In the evening, it should be the other way around: significantly less blue in the light, no extensive lighting. This prolongs the time it takes to fall asleep and suppresses the effect of melatonin—even with the smallest dose of light from the cell phone,” says Stefani.
How much light is good for our health?
As for how much light we actually need, “the recommendations of an expert committee
state that the light intensity should be a maximum of ten lux MEDI (Melanopic Equivalent Daylight Illuminance), three hours before going to bed,” says Stefani.
In other words, that’s the equivalent of the light from around ten candles at a distance of one meter before bed at night.
What about during the day? “There are different statements on this,” Stefani says. “Most experts say that 250 lux of daylight should be provided throughout the day,” says Stefani.
Here’s another recommendation: “You should be exposed to 10,000 lux for one hour,” says Stefani. “That’s bright, so you need a good light therapy lamp to avoid being dazzled.”
Understanding lux light measurements
Confused? For comparison, it helps to think about the light during certain months. In November in a northern location, 250 lux is reached outside shortly after sunrise, while 1000 lux is quickly exceeded in the morning. Around 10,000 lux is reached around midday. In foggy weather, the figure is around 5,000, which according to Stefani, is still around ten to a hundred times higher than inside a building. In sunshine, you can quickly achieve 50,000 or 80,000 lux.
In other words, during the day it is better to have more light and there is no such thing as too much; At night, it is best to dim down quickly as soon as evening hits.
And, if you’re wondering whether it’s not enough to sit by the window, the answer is: Not really. “Daylight is filtered through windows, so we should always aim for a daily walk outside if we can," says Stefani. Daylight also brings fresh air and the production of vitamin D into play.
Not all light therapy lamps are equal
Of course, there are currently more and more tools to maintain light-related well-being in the dark months. For example, daylight lamps or light showers. These are said to support the circadian clock and also stimulate the release of serotonin, thereby increasing concentration and well-being.
“Daylight cannot be replaced on a one-to-one basis, but daylight lamps or light showers are good aids to ensure well-being,” attests Stefani. A high-quality light is, therefore, important. “Ideally one with an LED similar to daylight,” he says.
Professor Henrik Oster agrees: “Even high-intensity daylight lamps (10,000 to 15,000 lux) are not comparable to the light intensities we experience on a sunny day.”
While infrared lamps are also currently praised by wellness influencers, science says that it doesn’t do much for the circadian rhythm. Although red light is great for blood circulation and therefore for the skin—which, yes, also has an effect on well-being—it has no confirmed influence on the internal clock.
Light harmony at home
As Drew Barrymore once said, “Nothing makes me angrier than ceiling lighting.” But how should we light up our homes for peace of mind? Helen Neumann, Director Lighting Design at the lighting company Occhio explains it this way: “The secret of good lighting lies in the clever selection and placement of luminaires. A successful lighting concept is characterized by the fact that the light follows the use of the room. Light is only used where it is really needed. Light zones are needed where people are eating, cooking, working, or reading, for example."
She recommends maintaining harmony between direct and indirect light: “Direct light falls downwards. Indirect light is reflected back into the room from walls or the ceiling. Wherever I want to open up or elevate the room, where I have communicative areas, such as at the dining table and sofa, I would also recommend indirect light. If I want to highlight a particular piece, direct light.” Coziness is even better. Think: candles and the warm, soft light from low table lamps versus “the big light” in the ceiling.
And in the bedroom? Neumann says it should be intuitive: “Warm light colors remind us of the quiet hours of the day, when the sun is just setting and the restful night slowly descends upon us. We let go of our thoughts and allow peace to enter us. These are strong associative fields that subtly give us a feeling of complete security and make us feel at ease.” According to her, really good lighting design is not just about designing light, but also about consciously designing dark zones. As is so often the case, the power lies in the balance—in this case that of light and dark.