Sunlight & Our Internal Clock
The Body’s Internal Clock: Circadian Rhythm
All the biological activity in the body is based on time. Every organ system, tissue, and cell in the body is encoded to be on a 24-hour pattern of activity tied to our sleep/wake cycle. We know this as our circadian rhythm.
Circadian rhythm controls every function in the body, whether it be directly or indirectly. The most important functions of our organ systems, metabolism, production of hormones and neurotransmitters are all orchestrated by our internal circadian clock. As a result, when our circadian rhythm is thrown off, all functions of the body are thrown off with it, opening us up to disease and dysfunction.
“The most important processes of every organ system are regulated by their circadian clocks”
“The body’s inner clocks are exquisitely tuned to environmental cues and optimized for the natural world. That also means they can be thrown off track by life in the modern world.”
Sunlight
Sunlight is one of the primary regulators of circadian rhythm, as it communicayes to the body what time it is in the 24-hour cycle. When sunlight enters our eyes, it essentially flips the body’s “on” switch. We become awake and full of activity — we eat, digest, release hormones, and manufacture energy. As the sun sets and darkness falls, the absence of light signals it’s time for the body to ramp down. Melatonin is released, preparing the body to sleep, fast, and repair itself.
Sunlight is not our enemy. In fact, the reverse is true. More and more studies show that sunlight is crucial and has much more positive affect on our health than originally thought. We know we need sun to produce Vitamin D (in conjunction with cholesterol lying underneath our skin), but the sun does so much more. It can lower our diabetes risk and prevent depression.
“The reason we have life on earth is because of the sun.”
Sunlight and Diabetes
Since the 1960s, diabetes experts have known that glucose intolerance and insulin sensitivity are on a rhythmic cycle throughout the day. They believe the hormone, melatonin, may be a contributing factor insulin sensitivity. Remember, the release of melatonin is triggered in the evening when the sun goes down, thus it’s affected by the natural light/dark cycle of Nature.
Exposure to sunlight in the daylight hours may also play a crucial role in insulin sensitivity. A study done in Brazil revealed that obese women, who received bright light therapy after they exercised three times a week for five months, showed a marked reduction in fat mass and insulin resistance compared to the control group of women, who did the same daily exercise, but were not exposed to the bright light therapy.
Additionally, another study done by the University of Geneva revealed that even small changes in light exposure — both in light and dark hours of the day — can significantly affect insulin resistance. According to Dr. Casey Means, this may explain why being exposed to light (artificial light) after dark increases a person’s chances of developing a metabolic disorder, like diabetes.
Sunlight & Depression
It’s well established that sunlight affects our mood, and therefore, our overall mental and metabolic health. We’ve heard of Seasonal Affective Disorder (SAD), where the reduced amount of sunlight in fall and winter can trigger depression in some people. This is because sunlight triggers the release the neurotransmitter, serotonin, which is our “feel-good” chemical that positively affects our mood. When exposure to sunlight is reduced, serotonin release is also reduced, and our mood suffers.
Studies also point to a reduction in appetite and blood sugar levels with increased serotonin.
A Deeper Look into Sunlight
Blue light is the specific part of natural sunlight that sets our body’s circadian rhythm and keeps us awake throughout the day. When photoreceptors in our eyes are struck by light, they trigger electrical impulses to the brain, specifically the suprachiasmatic nucleus (SCN), the master conductor of the body’s numerous functions. Like flipping the body’s “on” switch, sunlight triggers the SCN to initiate the proper biological activity in the morning.
Specifically, blue light causes the release of the hormone, cortisol, which is responsible for ramping up energy production in the body. In the morning, the amount of blue light emitted by the sun is very low, but as the day progresses, it increases, reaching its highest intensity at mid-day, around noon time. This makes sense because this is when we are most active . . . or at least should be. Blue light also affects the release of neurotransmitters and assists in the regulation of metabolism - two things we know have a profound effect on our overall health.
Why Does Blue Light Matter?
As we’ve seen, blue light affects our circadian rhythm, which is crucial in maintaining our overall wellness. However, when created artificially, blue light can become harmful in several ways.
Modern, man-made light sources (light bulbs, fluorescent lights, computer and phone screens) isolate the blue wavelengths to stimulate the brain and body for activity by increasing hormone and neurotransmitter production. This in turn artificially keeps the body “ramped up” and can drain and exhaust the body’s reserves over time.
Isolated blue light doesn’t occur in nature because near-infrared light, which is always present in large quantities in sunlight, naturally counter-balances high-energy blue light. In the name of “energy efficiency,” modern artificial lights have completely eliminated near-infrared light, as it is viewed as “wasted energy.” Thus, modern light sources are devoid of near-infrared light, causing intense blue light to be emitted, which is highly detrimental to the health of our eyes, cells, brain, and body as whole.
During the day, chronic exposure to blue light from man-made sources (light bulbs, fluorescent lights, computer and phone screens) can cause eyestrain, headaches, and fatigue. Over time, this exposure can even lead to retinal damage.
Chronic exposure to blue light, especially after sunset, has been proven to disrupt our body’s circadian rhythm. Since the circadian rhythm is a timing system that controls a variety of functions, the main effect of this phase delay can be seen in the suppression of natural melatonin production.
Chronic disruption of the circadian rhythm and melatonin production by exposure to blue light at night can lead to long-term health consequences as a result of a lack of cellular repair, in particular, increased degeneration of mitochondrial function. The majority of modern chronic illnesses are mitochondrial in origin, meaning they are due to a failure of natural energy production. Hence, it is critically important to protect our natural melatonin production by blocking blue light at night.
Chronic exposure to blue light, especially after sunset, has been proven to disrupt our body’s circadian rhythm. Since the circadian rhythm is a timing system that controls a variety of functions, the main effect of this phase delay can be seen in the suppression of natural melatonin production.
Chronic disruption of the circadian rhythm and melatonin production by exposure to blue light at night can lead to long-term health consequences as a result of a lack of cellular repair, in particular, increased degeneration of mitochondrial function. The majority of modern chronic illnesses are mitochondrial in origin, meaning they are due to a failure of natural energy production. Hence, it is critically important to protect our natural melatonin production by blocking blue light at night.