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How Sun Exposure Helps You Sleep
There’s growing scientific evidence connecting how much daily sun exposure we get to how well we sleep.
For a whole suite of reasons—from melatonin production to infrared exposure—the sun could be your best medicine for sleep. Let’s dig in!
Here, five ways the sun can help you sleep:
1. Morning Sun Exposure Boosts Melatonin at Night
According to Russel Reiter, PhD, one of the world’s most revered melatonin researchers, melatonin should be classified as a molecule, rather than a hormone—which you may have heard it called before.
Melatonin is a three-billion-year-old molecule that once activated biological changes in primitive organisms. Those changes allowed those organisms to adapt and evolve in harmony with the predictable cycles of day, night, summer, and winter, also known as circadian rhythms. For this same reason, melatonin remains fundamental to the healthy functioning of all life, including ours.
Research shows that in humans, darkness stimulates neurons in the hypothalamus that signal the pineal gland to secrete melatonin that supports sleep, rejuvenation, and detoxification.
Interestingly enough, your body makes melatonin during the day to release at night. A handful of studies have found that direct exposure to morning sunlight specifically increases the production of nighttime melatonin and supports better sleep.
In a study of 61 elderly folks, researchers found that exposure to direct sunlight between 8 a.m. and 10 a.m. for five consecutive days increased sleep quality.
In a 2001 study, morning light exposure caused evening melatonin production to start earlier (sometimes up to almost three hours earlier), which supports earlier bedtimes and more alignment with circadian rhythms.
Finally, in a review of 45 studies that evaluated the impacts of light exposure, researchers found that morning light supported better sleep.
2. Sun Exposure Also Boosts Daytime Production of Melatonin
Daytime melatonin production, which is different from nighttime melatonin produced by the pineal gland, helps mitigate damaging oxidation that is a byproduct of cellular energy production.
It turns out that the sun’s daytime red and infrared light stimulates a massive production of melatonin inside of each cell.
In fact, a whopping 90 percent of the body’s melatonin is produced this way and used to reduce oxidative stress. Accumulation of free radicals (that damaging oxidation) is linked to accelerated aging, fatigue, poor sleep, and a host of other health concerns.
In a study that measured free radical damage and cognitive decline from sleep deprivation, researchers found that near infrared light exposure increased cellular melatonin. They linked cellular melatonin to the repair of oxidative damage from sleep deprivation and the reversal of cognitive decline.
3. How Much Sun You Get Each Day Affects Sleep Quality
Serotonin, a neurotransmitter that supports stable moods, is also a precursor to melatonin. Scientists have known for decades that the more sun exposure you get, the more serotonin you produce, and, in turn, the more melatonin your body produces. More melatonin generally means better sleep.
Sachin Panda, PhD, the author ofThe Circadian Code and a leading expert in the field of circadian research, has compared the quality and quantity of sleep based on different amounts of daily sun exposure.
He measured sleep quality in study participants after they spent a week outside camping, as well as in participants who worked under shade, participants who worked indoors with lots of natural light, and participants who worked indoors under artificial light.
Working indoors under artificial light resulted in poor sleep. Working outside under shade or indoors with lots of natural light resulted in decent sleep. While camping and being exposed to full sun all day, resulted in deep and uninterrupted sleep.
According to some statistics, Americans spend 90 percent of their time under artificial light. Even in the winter, it’s important to get outside as much as possible to make up for a lack of natural light and sun exposure.
In a study on children, sun exposure and sleep, researchers evaluated more than 14,000 students from age 7 to 18 years old for sleep duration, sleep onset time, physical activity, time in the sun, and consumption of tea and coffee.
Sleep duration improved significantly with sunlight exposure and physical activity. Plus, sun exposure and exertion were correlated with earlier bedtimes.
In a recent study at the University of Colorado in Boulder, researchers found that reduced exposure to daytime sunlight and increased exposure to electrical lighting at night led to circadian disruption and altered sleep timing.
They performed two studies in which participants didn’t use any electrical devices or artificial lighting for a period of time. The first study showed a 100 percent circadian realignment after camping for one week, and the second study, which asked participants to camp for just a weekend, showed a 69 percent realignment with normal circadian rhythms.
4. Infrared Light Exposure Helps Sleep
According to one report, 70 percent of the photons, or light energy from the sun, are near infrared rays. The majority of the sun’s red and infrared light intensity is after sunrise and before sunset. Campfires are also a powerful source of red and near infrared light.
Near infrared light is next to red light in the visible light spectrum and while invisible, both red and near infrared light have been shown to support healthy sleep cycles, beyond the benefits described above related to melatonin production.
In a study with female athletes, the use of red-light therapy before bed improved their quality of sleep. Researchers concluded that red light offered a nonpharmacologic and noninvasive therapy to prevent sleep disorders after training.
Other studies have found that cellular energy production sparked by infrared and red light activates certain genes that may decrease symptoms of headache, cognitive impairment, sleep disturbance, anxiety, and depression.
Infrared light from the sun is the main producer of adenosine triphosphate (ATP). ATP is cellular energy.
During sleep, certain areas of the brain get a boost in ATP, which supports the Ayurvedic premise that we need energy to calm the nervous system down to sleep. Without adequate energy, the nervous system would stay wired and tired with little sleep. Ample energy, in the form of ATP, is needed for healthy regulation of the body’s sleep cycles.
ATP energy has the ability to both excite and sedate the nervous system, and both are needed for sleep balance. REM sleep, for example, requires more activating ATP, while deep sleep requires more sedative energy. Without adequate exposure to the sun and it’s infrared rays, ATP production can become compromised.
See also Circadian Rhythms 101
5. Vitamin D from the Sun Supports Sleep
The UVB radiation responsible for making pre-vitamin D on the skin is blocked by the atmosphere in the morning and afternoon hours. But UVB rays can penetrate the atmosphere when the sun is bright at midday during the summer months in the northern and southern hemispheres.
During winter months in America, the sun is too low in the sky north of Atlanta for UVB rays to penetrate the atmosphere, which makes it a challenge to get adequate vitamin D from the sun.
In a 2021 review, researchers estimated that more than 1 billion people around the world are vitamin D deficient.
According to a World Health Organization report, we shouldn’t be so afraid of sun exposure. Excessive UV radiation exposure accounts for only 0.1 percent of the total global burden of disease.
So, for the sake of your sleep and a host of other benefits, get some sun exposure.
During the summer months it is quite easy to get enough vitamin D with minimal sun exposure. To maintain healthy vitamin D levels, most adults need 3,000-5,000 IUs a day.
In a review of nine studies on vitamin D and sleep, researchers found that people with vitamin D deficiencies had a significantly higher risk for sleep disorders. They also linked vitamin D deficiencies to poor sleep quality, short sleep duration, and lack of sleepiness.
Vitamin D receptors and enzymes are found in several areas of the brain involved in sleep regulation. Vitamin D is also involved in the pathways of production of melatonin. Vitamin D deficiencies are also associated with restless leg syndrome, sleep apnea, and chronic pain, which can all disturb sleep.
I hope this research helps y’all to get outside, enjoy nature, and get a good night’s rest as a result!