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Human Centric Lighting: Ways to achieve a healthy biorhythm

Ways to achieve a healthy biorhythm


The latest trend in the field of illumination is called „Human Centric Lighting“(HCL) and deals with means to influence the natural biorhythm of people with artificial light. Now you may wonder – what is biorhythm anyway and what has it got to do with light at all? With the help of HCL and a few other tricks, quality of life can be improved significantly in various areas.

The Connection Between Biorhythm And Light: Set Your Biological Clock!

The sun was and has always been a central focal point for our biorhythm. It has been like this ever since the Stone Age: Each morning our ancestors came out of the cave and were stimulated by the sunlight. It made hunting and gathering a lot easier. Nature has arranged for us that we take a stroll outside and soak up sunlight. This same principle applies to reptiles. While they absorb the sun's rays over the skin in order to get their circulation going, for us, it is the eyes through which much is regulated.

There, the so-called ganglion cells have the task to filter the light and thus to stimulate the pineal gland in the brain. It controls our circadian rhythm by releasing of appropriate hormones: Melatonin for sleep or Cortisol for waking up. As the cells react particularly well to blue light, cool daylight has the greatest effect when it comes to waking up. If the day ends with a beautiful red sunset, the pineal gland switches to sleep. This is how our body clock is orientated by the position of the sun, regardless the annoying time change in Spring and Autumn.

effect of light in the brain


…is produced by the pineal gland of the brain and it's known as sleep hormone. It affects our biorhythm by giving the body the signal to sleep. The production is stimulated by cells in the eye that are sensitive to light. If the body is not given sufficient melatonin, sleep disturbances or lasting fatigue can occur.

Since the invention of the light bulb, the daily routine veers away more and more from the model day-and-night; moreover, due to shift work, jetlag and windowless factories, the human biorhythms gets a little mixed up. Unfortunately, our biological clock feels that it is day only at a brightness of 1,000 Lux, which is about as bright as it gets on a classic November day. In comparison, averagely lit interiors provide only 500 Lux. Thus, it is obvious to speak of man-made lack of light. The so-called "Winter Blues" leads to lack of energy, mood changes, a greater need for sleep or even ravenousness and gain in weight for sensitive people. To counteract this, it is advisable to use every bit of daylight especially during the dark season. Large windows are therefore just as appropriate as little walks in the afternoon.


The lack of light during winter time causes a shortage in the supply of vitamin D. The vitamin looks after our bones by ensuring that bone building calcium is absorbed from food, and by stimulating bone crafting directly in the bone with receptors. Therefore, vitamin D is not only essential for the growth period, but it also prevents diseases such as osteoporosis. Vitamin D is absorbed by the UVB sun rays over the skin. Experts recommend to go outdoors several times a week for about 15 minutes. Of course, longer walks are advisable when the sun is low during the darker winter season, or under cloudy skies.

The right dose of light can keep the biological clock in balance, despite Edison's great invention. For those who cannot charge their light battery with daylight only (and let's face it: who can?), they will find a remedy by Edison's heritage: The technology that has caused the problem, now offers a solution with the Human Centric Lighting.

Focus on Humans: Influencing Health With Biodynamical Light

What is the difference between biologically effective lights and ordinary lamps? In principle, it is the basic idea: it is focussed on humans, rather then only the room, hence the name "Human Centric Lighting". Instead of simply illuminating a room somehow, HCL wants to create the perfect light atmosphere, optimized for men. Depending on the area of application, well-being and mood, but also productivity, can be positively influenced. For this purpose, biodynamic lighting concepts were designed to counteract afternoon sleepiness at the workplace or to support the weakening biorhythm of patients with dementia.

Advice Against Winter Blues


Even on a rainy day the light outside is better than inside your house. Take in as much as possible.


There is nothing like healthy sleep. Even the best illumination is useless for the biorhythm when it has no sufficient rest.

Dawn stimulators

...emulate the morning light when it's still dark outside and gently support the waking up.

Therapy Lights ...are a substitute for lack of daylight: light showers support the biorhythm by its high brightness with up to 10,000 Lux.
Biodynamic Lamps

...imitate the color gradient of daylight in the course of the day.

Biological Light

...or full-spectrum light is able to simulate daylight better than ordinary lamps. Instead of only 3 colors, biological light is made of the 7 rainbow colors, just like the sunlight.


Mind the position of the light! The ganglion cells in the eye that transmit the signals to the circadian clock are located far down in the eye, just close to the lower eyelid. They react to light coming from above!

Since the connection between the light-sesitive cells in the eye and the pineal gland in the brain has been discovered a few years ago, biodynamic lights, dawn simulators and light therapy lamps are booming. They step in when the demand for daylight cannot be fulfilled for various reasons. Especially in the dark season, it is useful to fall back on these tools. If we do not spend enough time outside (and who wants to do that it in that dreadful weather), we practically remain in "biological darkness", which unfortunately prevails in the house all day. The biological clock is thrown out of balance, as the production of melatonin is not sufficiently suppressed by the reception of cool and bright daylight. Light is considered cool from about 4,000 Kelvin. A sunny day comes up to 12,000 Kelvin. A conventional incandescent lamp, on the other hand, has a warm light color of 2,700 Kelvin. The consequences of this deficiency are exhaustion, tiredness and a lack of vitamin D: light deficiency depression. Approximately 20% of people are affected; up to 5% suffer from severe symptoms.


So if you have to get up at 6, you can equip yourself with a dawn simulator that emulates the morning light and gently supports the awakening phase. For breakfast you can allow yourself a light shower. This is especially beneficial to the mind when everything is gray outside. The market also offers lamps with organic light. This means that the light comes with a larger color spectrum, which is comes even closer to natural daylight. Lighting fixtures, whose brightness and light color can be adjusted from 2,700 to 6,000 Kelvin, support the daily rhythm. Such biologically effective luminaires provide for the necessary cool and bright light in the morning and become warmer during the day. This way the release of melatonin in the evening is ensured. The effect is caused by the light color on the one hand and brightness on the other hand. These are the essential factors that influence the light receptors. If you want to surf for a bit with your smartphone before you go to sleep, you should check whether the screen color is adjustable, and in case of doubt, you should download apps for lighting control. They reduce the proportion of blue on the display: Too much cool light in the evening impairs a relaxing sleep.

Light Therapy:


Ideally in the morning. It is not advisable to do light therapy after 12 o'clock, as the level of the sleep hormone is pushed down which in turn can cause sleep disorder in the evening.

For how long?

Depending on brightness, up to an hour is recommended. At a brightness of more than 10,000 Lux, 15-30 minutes are sufficient.


About 7,000 Lux are suitable for therapy. The biorhythm reacts at about 1,000-2,000 Lux. It is also important to have a high blue component (which means a preferably cool light with at least 4,000 Kelvin and more) and that the incidence of light is upfront and from above.

Healthy Sleep – Healthy Biorhythm

Healthy sleep is just as important for a balanced biorhythm as sufficient light. The required amount of sleep strongly varies from person to person. Even scientists cannot provide a clear consent. The guideline for adults is about 7-9 hours of sleep, however, many people also feel comfortable with more or less.  The well-being is the most important indication. Numerous studies have shown that too little sleep as well as too much sleep can cause illness and lead to symptoms such as continuing fatigue, difficulties in concentration, and exhaustion.

The right amount of sleep is a great favour for the inner clock. The natural circadian rhythm is connected to daylight: in the dark, the melatonin release is stimulated, whereas it is suppressed particularly by cold-white light. Thus, for those who do not want to sleep completely in the dark, or want to read a little before going to sleep in the evening, the use of a reading light with warm white light is recommendable.

Lichtrezeptoren in Gehirn

„Careful with the last Facebook check before going to sleep: screens of smartphones and tablets emit cool light that impact a restful sleep negatively. New apps are able to reduce the proportion of blue in the light”

For waking up, cool daylight is helpful, but especially during the winter time artificial light can help as well. Lighting fixtures with a cool light colour are suitable. Especially dawn simulators counteract the winter blues. They gradually light up the room by an automatic dimming option and thus simulate dawn light and sunrise. They help the body to adapt to the upcoming morning and wake you up gentlier than ordinary alarm clocks. When days are getting shorter, they help pushing down the melatonin level in the morning, even though it is still dark outside. A lot of bright light in the morning is just the right means for starting the day fit and in a good mood.

Human Centric Lighting in The Office

Checklist for Biologically Effective Light at Work:

  • Brightness: higher levels of illumination achieve a positive biological effect
  • Direct/Indirect: equal to daylight, light should be emitted both with direct lamps and indirectly over illuminated surfaces
  • Direction: Light achieves the best effect when the incidence of light is from above and front into the eye
  • Color: the biorhythms reacts to blue light - the cooler the color temperature, the better. A high Kelvin number makes you awake and active.

With the right illumination, you can create the optimal light at home, which supports the daily routine and has a positive effect on the biorhythm. But HCL is also used in other areas. At the workplace, for instance, rarely there are sufficient windows for all employees, so that many people have to sit in biological darkness. This is of course not beneficial to work. By using biologically effective light, the biological clock can be set to the correct mode. Light therapy lamps at the workplace for the small light shower are a great option for the break. This way the afternoon sleepiness can be minimized and the performance of your colleagues immproved. However, breaks should not be canceled, just because the cool light pushes the power!

gesundheitsfördernde Beleuchtung im Büro

An example from real life shows the consequences of the disregard of the biorhythm: An automobile manufacturer has changed their illumination and provides a cool light of around 5,000 Kelvin throughout the night shift for their employees. As a result, productivity rose by 15% because people were able to work more concentrated throughout the night. However, after a few weeks the rate of illness increased eventually. The biorhythms of the employees had no way to settle somehow: The employees left the factory hall with cool indoor light in the morning to a cool daylight and then went to bed at home. The biological clock, however, thought of anything but sleep at that moment. Due to the constant cool light, the melatonin level was permanently suppressed and thus, a restful sleep was hardly possible. It made people sick in the end. Even without a night shift, a certain balance should be considered. For instance: The dent in the performance curve after lunch should at first be accompanied by warm light to settle. After a break, work can be boosted again with cool, activating light.


„The dent in the performance curve after lunch should at first be accompanied by warm light to settle. After a break, work can be boosted again with cool, activating light.“



The best results in the illumination of the workplace are achieved by a combination of indirect and direct light sources. This is similar to daylight on a sunny day by a lively interplay of light and shadow. The light atmosphere is more pleasant for the eye and appears activating. This kind of light also makes people feel more comfortable.

Human Centric Lighting in Medicine

In medicine, HCL has gained more importance in past few years. On the one hand, it is of course important that people have no light deficit, even if they are not mobile. On the other hand, it is indispensable that people don't fall due to bad light, and that uncertainties in general are minimized by sufficient light. Biodynamic light is a great help in everyday life for people whose daily routine got confused by diseases such as dementia. It is used in the care for elderly. Even artificial light is created as basic illumination, which birghtens the surroundings with a combination of direct and indirect light. Colors, which reflect the blue light parts well, support the effect of the light. The light color changes during the day from cold light in the morning to warm light in the afternoon and evening. Thus the receptors of the patients send the correct signals to the biological clock, which will be stabilized again. Symptoms such as morbid restlessness and sleep disturbances of the patients can be defeated and the natural biorhythm supported. In practice, the lighting concept has improved the quality of sleep by 75%.

Human Centric Lighting in Education And Other Areas

In addition to the office sector and medicine, the positive effects of biodynamic lighting are also used in education. Some schools are, for instance, equipped with lighting systems that can support concentration on demand. Early in the morning, the teacher can use the "activate" function to make their still sleepy students wake up by sending the right signals with medium brightness and very cool light. The setting "concentrated work" is particularly suitable for tests or difficult tasks: brightness and color temperature are therefore similar to daylight and have a positive effect on the attention. Warm and dimmed light in the "soothe" function lets the students settle during unrest, after tests or demanding school hours.

As part of a research project, schools were observed at the university hospital in Hamburg and based on comparative data it was ascertained that children with concentration stimulating light showed better performances with a lower error rate. Even their sleep pattern changed as a result: They went to bed earlier and were rested better in the morning.

On the basis of these studies, similar light concepts can be applied to universities and libraries. In addition, Human Centric Lighting is also gaining importance in the field of hotel business, trade and industry.

effects of human centric lighting

Clinical Study About The Biodynamic Efficiency of Light

The German enterprise Durable has specialized in the production of biodynamic lighting at the workplace with the foundation of the brand "Luctra" a few years ago, establishing itself among other great names in this branch. The manufacturer commissioned a clinical study in 2014, which was conducted and carried out by the somnologist Dr. med. Dieter Kunz. The study demonstated the biological effectiveness of dynamic lighting. 16 individuals were exposed to different lighting conditions during a test period on five evenings, including normal lighting for control and lighting with the Luctra desk light with various light colors. The biological activity was measured using the melatonin content in the saliva, while the participants were additionally asked for their subjective perception of well-being. As a result, production of melatonin was stimulated upon the illumination of 6,000K (cold-white) and 3,800K (cold to neutral-white), whereas no significant change could be measured for other lighting situations with warmer light colors.

The participants rated warmer light as more pleasant than cool light. However, they also preferred the warm light of the Luctra luminaire to the light of reference lamps. The cold-white light was considered too bright, which is understandable, considering that the study was carried out in the evening: the body being biologically stimulated at this time of the day makes no one feel comfortable. This allowed Luctra to demonstrate the biological effectiveness of its lamps. Proper illumination is important to health and well-being, as well as to productivity at the workplace. On the basis of this premise, Luctra has developed a lighting concept that re-evaluates the quality of the workplace. The luminaires simulate the color spectrum of sunlight and thus, acting as daylight, have a stabilizing effect.

Good light is of great importance to health and well-being, but also to productivity at work.

The Luctra table light has several LED boards, which create continuously variable light colors from warm white to cool white. It can be adjusted to change its light color biodynamically during the day. An intuitive control element allows the adaption to the individual rhythm. The lamp was designed to be a high table lamp in order to direct the incidence of light from above and frontal into the eye to unfold its full effect. In addition, the energy-efficient LED technology from Luctra has an ideal light distribution for the workplace with a high illumination of up to 1,000 Lux.

Luctra und Grimmeisen Onyx Leuchten

Another German manufacturer of biodynamic lights is Grimmeisen. The company was founded in 2007 and has designed the Onyx Air pendant light in a 2-year design and development work. This lamp is ready to meet the constantly increasing demands in the fields of health, digitalization and networking. Furthermore it provides corresponding functions for smart home and the possibility to adjust the light temperature by gesture control. This way, the biologically effective light is not only restricted to the desk, but can be applied to all rooms. The minimalist design of the ultra-flat pendant light fits to almost any environment.

Even renowned manufacturers with their well-known designers have recognized the trend and are launching appropriate models on the market. Artemide, for instance, has expanded the successful Tolomeo line with a "Tunable White" model with which the light can be adapted as required in the light color.

Human Centric Light in The Future

There are various fields of application of Human Centric Lighting and the possibilities are almost unlimited. LED technology provides us a new lighting tool that can be used to realize entirely new concepts. The trend promises exciting developments for the future. It will also define new standards and will have a lasting effect on areas such as workplace lighting.

By then, we can use these small tools to overcome the winter blues. Keep in mind: The biorhythm is mostly pleased with sunlight and healthy sleep. Biodynamic light and therapy lamps should at best complement and not replace daylight. The next spring is on the way!

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