We often associate our health with how we eat, drink, and exercise. And while these things are all major contributors to our overall well-being, there is scientific evidence that proves viewing and absorbing sunlight can positively impact our health in a variety of ways. Andrew Huberman, American neuroscientist and tenured associate professor at Stanford University School of Medicine, discusses the science and impacts of sunlight on his podcast, Huberman Lab Podcast.
I did the hard work for you and found the key points from this podcast. There is a lot of information to be digested here, but I will break it down in the simplest way that I can. I will also link some information such as the peer reviewed studies that he refers to. Sunlight can improve your mood and your sleep, enhance alertness, modulate hormone levels, and impact your cells, tissues, and organs.
The Physics of Light
To understand how sunlight can optimize your health, Huberman explains that first you must know a little bit about the physics of light. Light is electromagnetic energy that is traveling in wavelengths. Light has many wavelengths, some being shorter or longer. The rainbow is the visible spectrum of light, but there are other wavelengths of light that we can’t see. Some animals can view certain wavelengths of light that humans cannot. For example, snakes can see an infrared energy radiating off you.
Light absorption through our skin plays a big role in our health. Ultraviolet light can positively impact us. Viewed for just a few minutes each day or landing on the skin for a few minutes each day, it can offset a lot of pain. Different wavelengths of light can penetrate tissues to different depths. UV light has short wavelengths and can’t penetrate as much into the skin, whereas red light or infrared light can penetrate through tissues, even down to your bones. An important concept to understand, Huberman says, is that “particular wavelengths of light can be used to stimulate the function of particular organelles within particular cells within particular organs of your body.”
The Biology of Light
For those who aren’t big on science lessons, I promise this will be worth it. There are a few more points to understand before getting into the benefits of light exposure and absorption. Every biological function of light has to do with the absorbance or reflectance of light, or light that passes through something. If light can access the cells of your body, it will change the way those cells function. The ways in which light can impact your body can be direct or indirect, and slow or fast. Skin absorbs light and also has pigment, called melanin. Tanning is an example of absorbing UV light specifically; we can see how our skin cells react — we get darker.
You have a biological calendar that exists within your body which uses hormones that are released into your brain and body each day and night, as a way of knowing where you are in the 365 day calendar year. This is known as Circannual Rhythms. The sun travels around the earth, and depending on where you live and the time of year, you will get different amounts of light each day on average.
Light hitting the eyes is absorbed by cells, which communicate with your brain. The pineal gland in your brain is the primary producer of a hormone called melatonin. Light activates these cells which shut down the production of melatonin. People in the northern hemisphere get more melatonin release in the winter months (less light = more melatonin) than you do in the summer months (more light = less melatonin).
Melatonin makes us sleepy, impacts our mood, affects bone mass, and suppresses puberty.
Melatonin has a role in making us sleepy each night, but it also does many other things. It has regulatory effects and protective effects. Melatonin can positively affect bone mass. It also affects the maturation of ovaries and testes by suppressing puberty. The point of all this being that it’s important to get the proper amount of sunlight each day, because light powerfully inhibits melatonin.
In the summer months, when days are longer, we would all benefit from getting more sunlight in our eyes. In the winter months, it makes sense to spend more time indoors to stay warm. But for those with seasonal depression, you can use sunlight viewing early in the morning to help offset this.
Light and Mating Behavior
Light impacts our behaviors in terms of mating and our levels of testosterone and estrogen. Animals and humans tend to seek out a mate during the longer days of spring and summer. Males and females both produce testosterone and estrogen, just at different levels, and these hormones are important for the desire to mate and mating behavior. Exposure to UV blue light can trigger increases of testosterone and estrogen, as well as the desire to mate. What’s different about this is that it’s not driven by exposure of light to the eyes, but rather the skin. This is because the skin is an endocrine organ, which produces hormones.
In a study published in 2021, about skin exposure to UVB light, humans and mice were studied. The basic finding of the study was that when mice or humans were exposed to UVB light, if they received enough exposure of light to their skin, there was an increase in testosterone and estrogen, and the mice sought out mating more. There was also an increase in the weight and size of the testes and ovaries. For humans, they didn’t observe the size of the gonads, but studied the psychological effects of light exposure. The findings were that in men, there was enhanced female attractiveness, and increased receptiveness (desire to mate) in both males and females.
This increases a woman’s chance to become pregnant.
They also found effects on fertility, especially follicle growth. UVB light exposure enhanced follicle maturation, meaning that more healthy eggs were produced. This increases a woman’s chance to become pregnant.
Light Exposure and Pain Tolerance
Our tolerance for pain actually varies across the year, and is increased in longer day conditions. Huberman refers to two different studies. In one, they found that even one exposure to UVB light changes the output of particular hormones. UVB light exposure increased the release of beta-endorphins, which are basically natural pain-soothers that the body produces (endogenous pain killer). In the second study, they found that light landing on the eyes and captured by specific cells communicates with particular brain areas and prompts the release of these endogenous opioids which soothe you and help you have a lesser perception of pain. Basically, light exposure can give you a higher pain tolerance.
Some tips Huberman gives on receiving the benefits of this UVB light are as follows:
View sunlight as much as you can each day, even on cloudy days.
Artificial UVB light is not as effective as sunlight.
Don’t use blue-light blocker glasses or lenses all day, and don’t use them outside. It’s best to use them only in the evening and nighttime.
Look at sunlight in a safe way – meaning don’t do anything that causes pain.
For those who have a drop in energy during winter months, a SAD lamp or LED lighting panel is beneficial.
UVB Light and Immune Function
There are studies that show how spleen and immune function can be impacted by exposure to light. Your brain is actually connected to your spleen. UVB light hitting the eyes can trigger activation of neurons within the sympathetic nervous system. With sufficient UVB light to the eyes, a particular channel within the nervous system is activated, which causes our spleen to deploy immune cells and molecules that combat infection.
As Huberman explains, we associate summer months with fewer infections floating around, but there aren't actually fewer infections going around, rather we are better at fighting those infections during the warmer months. In the winter months, we should be especially concerned with accessing UVB light to enhance our spleen function.
Wound healing is faster when we are getting sufficient UVB exposure.
It’s also known that wound healing is faster when we are getting sufficient UVB exposure. Another interesting fact is that our skin cells turn over more when we get more exposure to UVB light. If you notice during months with longer days that your hair and nails grow faster, this is why.
Light and Mood
Huberman emphasizes the importance of getting light as much and as early in the day as possible because this will positively impact your mood. Along with this, avoiding UVB light at night is a way we can prevent a certain internal pathway that can turn on depression. Specifically, avoid UVB light from artificial sources from 10pm to 4am. And for those with mild depression in general, it’s very important to avoid artificial sources of UVB light starting in the evening.
In a study with a group of young adults, some were placed in a room with no light, and others in a dimly lit room. It was found that even when someone sleeps the whole night through, if the room they’re sleeping in has too much light energy, it can go through the eyelids and increase the sympathetic nervous system activation, and disrupt metabolism and cardiac function.
Infrared Light and Skin
Long wavelength light such as infrared light and red light is able to pass through surfaces such as the skin and change the metabolic function of the cells. Low level light therapy with infrared light has been proven to be effective as a treatment for acne and other skin lesions. Light therapy can also aid in wound healing, getting scars to disappear, and removing patches of pigmentation. Dermatologists often use red light therapies to help improve their patients’ skin or to help with anti-aging.
Light and Vision
Not only does light have ways of helping our skin, but it can also help improve our vision. Huberman goes over a study where test subjects of various ages viewed red light at a certain distance and amount of time per day for several weeks. The major findings were that in individuals 40 years or older, there was an improvement of visual function, specifically a 22% increase in visual acuity. An important takeaway from this information is that viewing red light and near-infrared light at a safe distance, for just a couple of minutes each day, provided a reversal in the aging process of these neurons.
If you want to create your own red light therapy, Huberman explains that you can take a bright flashlight and cover it with a film or filter that would only let long wavelengths pass through, or you can purchase a red light unit. It’s important to make sure that it’s not so bright that it damages your eye. He says a rule of thumb is that if it's painful to look at, it’s too bright.
This might seem like an overload of information, but it just goes to show that viewing and absorbing sunlight has a wide range of impact on the human body. Light has a direct and indirect effect on the body that can affect your mood, pain tolerance, immune function, skin, and vision. There are modern and artificial ways to get exposure to light, but taking in natural sunlight seems to be the best form of light you can receive.
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