Light is the basis for all life. Plants use light for photosynthesis, and the oxygen they release as a byproduct is what allows us, and other living organisms, to thrive on this planet. Light also directly influences the hormonal activity and sleep cycles of organisms and affects the function of cellular powerhouses, the mitochondria. Plants, for instance, time their growth and blooming cycles based on changes in light.
When we take a closer look at how light affects humans, we discover that its influence is far greater than we traditionally thought. In fact, light is one of the most significant factors affecting health and weight management, alongside diet and exercise. Perhaps the most well-known effect of light on our bodies is its impact on our internal clock and sleep-wake cycles. Melatonin, often referred to as the "sleep hormone," is secreted in alignment with our circadian rhythm, increasing in the dark and decreasing in the presence of light. Melatonin not only prepares us for sleep, but also serves as a potent antioxidant and regulates the production of other important hormones, such as growth hormone, prolactin, thyroid hormones, estrogen, and corticosteroids like cortisol.
The Role of Blue Light in Melatonin Production
Melatonin secretion is particularly sensitive to blue light, which surrounds us constantly. Sources of blue light in varying intensities include the sun, digital screens, electronic devices, and nearly all artificial lights, from incandescent bulbs to LEDs. Blue light inhibits melatonin production, lowering its levels when blue light exposure is high and increasing them as blue light decreases. The impact of blue light on melatonin is dependent on both the intensity of the light (measured in lux) and the duration of exposure.
For optimal functioning of the body's internal clock, it is essential to receive sufficient blue light exposure in the morning and during the day while minimizing exposure during the evening and night. A daily exposure of at least 15 minutes to light with an intensity of 10,000 lux or more is considered beneficial. Conversely, even a small exposure of 10 lux in the evening can disrupt sleep quality. A good rule of thumb to support melatonin production is to minimize blue light exposure at least an hour before bedtime.
Examples of Light Intensities from Various Sources:
Sunlight: 20,000 – 120,000 lux
Office building lighting: 300 – 500 lux
Home lighting: approx. 50 lux
Natural healthy lighting design
Natural Light
The best lighting option for healthy lighting design is natural light. Buildings should be positioned to allow as much daylight as possible to enter the space. In the Northern Hemisphere, large windows should be placed on the southern side of the building, where the sun shines the most. Living and working spaces, such as living rooms and kitchens, should be situated on the southern side, while sleeping areas are better placed on the darker northern or eastern side. If desired, bedrooms can be placed on the eastern side with large windows to allow the sunrise to naturally wake you. The further you are from the equator, the more sunrise and sunset times will vary throughout the year, making it difficult to rely solely on natural light for regulating waking times all year round. Windows should be incorporated as much as possible into the building's design, as natural views reduce stress levels, especially in nature-surrounded buildings.
In the Southern Hemisphere, this principle works in reverse. Large windows and living spaces should be positioned on the northern side of the building to maximize sunlight, while sleeping areas should ideally be placed on the southern or eastern side to create darker, cooler spaces. Note that in hot climates one should also take in account the heating effect of the sun, so direct sunlight might not be optimal/suitable.
Skylights are also an option to bring natural light inside, but they come with the risk of leaks, so careful planning and installation are crucial to minimize this risk. Blinds are good way to regulate the amount of light and heat entering the home. Additionally, blackout curtains are a great choice for bedrooms to block out light completely.
Artificial Light
In modern construction, energy efficiency is a significant trend. This has led to the increased use of various energy-efficient solutions, such as LED lights. While energy saving is important, there is a downside. The light spectrum humans have evolved under is natural incandescent light, also known as "glowing" light. This type of light is produced when an object’s temperature rises high enough to emit light. Examples of natural glowing light are sunlight and fire. Producing this type of light requires a considerable amount of energy. To improve energy efficiency, modern lights often remove specific wavelengths, typically the longer ones like red and infrared light, which produce a lot of heat.
Red and infrared light, however, are essential for our health. Unlike blue light, which can cause oxidative stress in cells, red light promotes cellular repair and healing. Studies have shown that red, near-infrared, and infrared light can support wound healing, reduce inflammation, and improve skin health. This red-infrared spectrum also plays a significant role in mitochondrial function, boosting energy production in cells, which has a broad range of health benefits, from enhanced muscle recovery to improved cognitive function.
Infrared light, particularly near-infrared (NIR), penetrates deeper into the tissues and has been linked to improved circulation, muscle relaxation, pain relief, and faster recovery. It stimulates the production of nitric oxide, which can improve blood flow and oxygenation of tissues. Additionally, it has been shown to have neuroprotective effects and might help mitigate the effects of degenerative diseases.
In summary, while blue light exposure should be minimized, especially in the evening, red and infrared light should be encouraged in our environments, particularly in the evening, as they help promote relaxation and support cellular repair.
When selecting artificial lights for home environments, the ideal solution is to choose lighting that mimics natural glowing light, which includes the full spectrum of visible light and some infrared. Incandescent and halogen lights are good options. LED lights can also be adjusted to include more red light, but care must be taken to avoid flickering and other negative effects associated with lower-quality LEDs.
In sleeping areas, it’s best to avoid all blue light-emitting bulbs. Good options for bedroom lighting include salt lamps and LEDs with warm, red or yellow tones. If it’s not possible to create a sunset-like dimming effect (reducing blue light) with lighting, it's advisable to start turning off lights in the evening and to use blue light-blocking glasses.
White LEDs, CFLs, and fluorescent lights should be avoided. They primarily emit blue light, generate electromagnetic fields (EMFs), and tend to flicker.
FLICKER & ELECTROMAGNETIC RADIATION (EMFs)
Flicker is a rapid and often invisible variation in light intensity caused by the way modern lighting systems operate. While the flicker may not always be consciously perceived, the brain is highly sensitive to it. Prolonged exposure to flickering light can cause eye strain, headaches, visual fatigue, and even migraines. Flickering lights can also increase cognitive stress, disrupt focus and mental clarity, and may lead to mood disturbances over time. The human nervous system becomes stressed when attempting to compensate for flicker, which may increase overall sympathetic nervous system activation and stress levels.
In addition to flicker, certain lights, LEDs, fluorescent and CFL lights can emit EMFs, which are another concern. EMFs are invisible areas of energy that are emitted by electrical devices, including light bulbs. Prolonged exposure to EMFs from lighting and other household electronics has been associated with various health complaints, such as sleep disturbances, fatigue, and even neurological issues in sensitive individuals. Long-term EMF exposure is also suspected to contribute to cellular stress and may negatively affect the body's endocrine system, impacting hormone production and sleep patterns.
By minimizing exposure to flickering lights and EMF-generating light sources, and opting for more natural lighting options, we can create a healthier environment that reduces both physical and mental strain. Whenever possible, use incandescent, halogen, or high-quality LED lights that offer full-spectrum lighting with minimal flicker and EMF emissions.
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