Understanding Light: The Foundation of Life
Light is an essential element of life on Earth, influencing everything from the growth of plants to the regulation of human biological functions. At its core, light is electromagnetic radiation, a form of energy that travels in waves. These waves vary in length, creating what we know as the light spectrum. The human eye perceives only a small portion of this spectrum as visible light, ranging from red to violet. However, light also includes invisible wavelengths such as ultraviolet (UV) and infrared (IR), which, though unseen, have significant impacts on our health and environment.
Light is also characterized by its color temperature, measured in Kelvins (K). Warmer light, like that of a sunset, has a lower Kelvin value (around 2,700K), while cooler, blue-enriched light, similar to daylight, has a higher Kelvin value (6,500K or more). This temperature influences how light affects our mood, alertness, and overall biological processes.
The Light Spectrum: A Range of Wavelengths
The light spectrum encompasses a wide range of wavelengths, each corresponding to a different type of light. The visible spectrum, the light we can see, ranges from the longer wavelengths of red light to the shorter wavelengths of violet light. Beyond visible light, the spectrum extends to ultraviolet (UV) light, with even shorter wavelengths, and infrared (IR) light, with longer wavelengths. Each part of the spectrum has distinct properties and effects on biological organisms.
Shorter wavelengths, such as blue and UV light, are particularly significant for their impact on biological processes. While blue light plays a crucial role in regulating our sleep-wake cycles, excessive exposure to blue light, especially from artificial sources, can lead to various health issues.
Artificial Light: A Double-Edged Sword
With the advent of artificial lighting, humanity gained the ability to extend productive working hours beyond sunset. However, this technological advancement has also introduced new challenges, as throughout evolution, we have never been exposed to this kind of light during the hours after sunset. Unlike natural sunlight, which includes a full, balanced spectrum of wavelengths, artificial light often skews heavily towards shorter wavelengths, particularly blue light in the range of 400-500nm. Devices such as smartphones, computers, and LED lighting emit high levels of blue light, which heavily disrupt our natural circadian rhythms, increases oxidative stress, suppress melatonin and ultimately leads to metabolic dysfunction.
Circadian Rhythm: The Body’s Internal Clock
The circadian rhythm is our body’s internal clock, governing the most vital biological functions such as regulating body temperature, growth hormone and cortisol release, alertness and sleep. For hundreds of thousands of years, human evolution was shaped by a natural cycle of daylight and complete darkness after sunset. This absence of light during the evening hours was crucial in shaping the preparation of sleep in order to heal and restore throughout the night in total darkness.
Circadian Rhythm: The Body’s Internal Clock
During the day, exposure to natural light from the sun dictates all metabolic functions of our organism. When to wake up, to be alert, to be at peak athletic capabilities. These were all vital to ensure the survival of our species. As the day transitions to evening, the reduction of blue light signals to our brain that it’s time to prepare for sleep, leading to the production of melatonin, the hormone responsible for inducing sleep and restoration. However, when we expose ourselves to artificial blue light during the evening, this natural cycle is disrupted because this is not what happens in nature. The brain perceives this light as daylight, delaying the release of melatonin and disrupting the sleep-wake cycle.
The Role of Melatonin and Blue Light in Mitochondrial Health
Melatonin is often recognized for its role in regulating sleep, but it’s also one of the body’s most powerful natural antioxidants. As our cells produce energy, primarily through the mitochondria, free radicals are created as a byproduct, similar to the smoke when a candle is burning. These unstable molecules can cause oxidative stress, leading to cellular damage. Normally, melatonin steps in to neutralize these free radicals, protecting our cells and mitochondria from harm. However, when exposed to artificial blue light, especially after sunset, melatonin production is significantly suppressed.
This suppression has far-reaching consequences. Without adequate melatonin, the body’s defense against oxidative stress is weakened, leaving cells and mitochondria vulnerable to damage. Over time, this oxidative stress impairs mitochondrial function, reducing their ability to produce the energy our cells need to function optimally. This leads to chronic fatigue, slower recovery from exercise or injury, and overall decreased vitality.
Moreover, malfunctioning mitochondria are linked to a range of long-term health issues, including neurodegenerative disorders, cardiovascular disease, cancer, and accelerated aging. For athletes, this increased oxidative stress can result in a heightened susceptibility to injury. The cumulative effects of reduced melatonin and mitochondrial dysfunction make protecting your body from excessive blue light exposure crucial—not only for sleep, but for maintaining cellular health, energy levels, and long-term well-being.
Cortisol and Blue Light: An Evolutionary Response Gone Awry
Throughout human evolution, our bodies have developed sophisticated mechanisms to protect against the harmful effects of ultraviolet (UV) radiation. One such mechanism involves the detection of short-wavelength light, particularly blue light, which often signals the presence of UV radiation in natural settings. Because UV is invisible for the human eye, the presence of blue light, especially from natural sources like the sun, triggers a protective response within our body. This response includes the release of stress hormones such as cortisol, which prepares the body to counteract potential damage from UV exposure, like sunburn. Cortisol helps reduce inflammation and readies the body for increased activity, such as repairing skin cells damaged by UV rays.
However, in today’s world, where we are constantly exposed to artificial blue light from screens, LED lights, and other sources, this evolutionary response has become problematic. Unlike sunlight, artificial light isn’t paired with UV radiation, yet it triggers the same biological response within our bodies. Over time, this contributes to a range of stress-related health issues, including cardiovascular disease, anxiety, and weakened immune function. What was once a beneficial response to UV exposure has, in the context of today’s environment, become a contributing factor to the modern epidemic of chronic stress and its associated diseases.
The Importance of Managing Light Exposure
As you see, the impact of light on our health is more far-reaching than you might have thought. Constant exposure to artificial light, particularly blue light at the wrong times, disrupts not just our sleep but also our metabolic processes, stress responses, and cellular function which then expands into virtually every domain of our lives. Managing light exposure is critical to protecting our circadian rhythm, supporting melatonin production, and reducing oxidative stress. At Sonder, we are committed to helping you navigate these modern challenges with our advanced eyewear solutions, designed to safeguard your health and well-being in a world dominated by artificial light.
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Learn more about the science of light and people who have shaped the vision behind SONDER.