Researchers Discover Vision is Required for Green Light Benefits
Scientists have known green light has health benefits, but they weren't sure how we received them
Hiya!
If you have any siblings, you likely know that it doesn’t matter how old you are, siblings are always siblings. A while back, my brother (whose almost 40 years old) got me one of those Smart multi-colored light bulbs that links to my Google Home thing. Whenever he comes over, he finds great joy in turning it to red, blue, or whatever color he feels like, then runs away with an evil cackling laugh.
Sigh, brothers are so annoying.
The first time he did it, I realized the light was more a gift for him than for me. After all, why would I ever need a pink or orange light on? Meanwhile, he finds it hilarious to change the color. But I recently came across the study I’m telling you about today, and now I wonder if perhaps I should spend more time with my light turned green.
Phototherapy
No one knows when the idea that light has healing properties has been around. Obviously, we, and presumably all our human ancestors, understood the power of sunlight, but now we also know that exposure to specific colors can yield certain effects.
Over the last decade, especially, researchers have racked up study after study showing that exposure to specific intensities and wavelengths of light help manage pain for anything from fibromyalgia to lower back pain.
Using light to heal or relieve pain is called phototherapy or light therapy. While most help with pain management, many colors have different uses and influences on us. Red light is the only color that doesn’t dilate our pupils. It’s also good for eczema, psoriasis, and wrinkles.
While blue light can improve many skin conditions, including acne, jaundice, and non-melanoma skin cancers, some studies suggest prolonged exposure can increase signs of aging, such as wrinkles. However, research also suggests that blue light helps us calm down faster after feeling angry, but it also messes with our circadian rhythm and can prevent us from sleeping.
But less well known are the impacts of green light and the mechanisms mediating them. See, research shows that green light has a pain-relieving and emotionally calming effect, but how it happens was unknown.
The Power of Green Light
Green is one of my favorite colors and just so happens to have a lovely list of physical and emotional benefits. For instance, green LED light has cosmetic benefits, including smoothing skin pigmentation like broken capillaries, sun spots, and dark circles.
Meanwhile, additional studies over the last few years indicate that green light is especially beneficial for anyone who suffers from migraines. It eases light sensitivity and is one of the few colors that doesn’t exacerbate migraine pain. Other research suggests that, unlike blue lights, green light helps us fall asleep faster.
Pain relief is another significant benefit of green light though researchers didn’t know how this interaction occurs was a bit of a mystery. That is until a team of researchers figured out that the effects of green light come not from the light’s interaction with our skin but with our vision.
The Studies
According to the paper, previous research has shown that opaque contact lenses block the analgesic effect of green light in mice, suggesting that vision has a vital function. A team of researchers at Fudan University in Shanghai grew curious and decided to figure out the relationship. To do so, they performed three animal experiments to learn more about the part the visual system plays. Then they published the results in the journal Science Translational Medicine.
Experiment number one
They began with a two-part test. First, they induced arthritis in one of the mouse’s paws. Then they confirmed that green light exposure helped relieve the pain. Part two included injecting a chemical that caused degeneration of the photoreceptor cells in the mouse’s retina. Afterward, the mice’s anesthetic effects from the light vanished.
As a follow-up, the researchers found that only the cones — the photoreceptors required to see colors — are needed to experience pain relief. In contrast, rods help us see in low-light conditions and are only partly necessary.
Experiment number two
Now that they knew which part of the eye is required for the animal to receive the light’s benefits, the researchers wanted to figure out which brain regions were involved. To do that, they traced the neural pathway between the retina and a sub-region of the thalamus (sensory info and pain receptor) called the ventrolateral geniculate nucleus (vLGN), which receives input from the eyes.
When the scientists obstructed the vLGN cells, the pain relief from the green light disappeared too. Conversely, activating the vLGN cells in the retina opened the pathway, and the anesthetic effects returned. This suggests a path in the brain from the retina to the vLGN cells is required for the pain-relieving results of green-light therapy, as is a functional primary visual cortex.
Experiment number three
This part gets a little complex, so bear with me. See, even though the vLGN is tiny, it has lots and lots of neurons that synthesize and secrete a neurotransmitter called gamma-aminobutyric acid (GABA). This amino acid helps your nervous system chill out. Well, the researchers noticed a subset of neurons that also synthesized enkephalin, a pain-relieving peptide, which, they discovered, is necessary for the analgesic effects of green light.
With this information, the researchers conducted their last experiments and found that the visual pathway in the brain is vital to feel the pain-relieving effects of green light. They suggest there’s also a certain classification of secondary retinal ganglion cells required too, which receive input from the rods and cones.
Perspective Shift
First, let me say that while I understand the rational reasoning behind scientific animal experimentation, I don’t support it. It makes my insides hurt just thinking about it. But I have to admit their results are intriguing.
I mostly associated the health benefits of light with its interaction with our skin, but I’ve spent far less time considering light’s impact on us visually. Then again, I suppose it shouldn’t be too surprising considering interior designers know well how the color of a room can influence our moods. So it’s not much of a leap to assume colored light would too.
In fact, I wonder how much of these results are because of the color and not the light itself. After all, it seems the benefits come from seeing the green light rather than, say, absorbing it. Don’t we find similar results after spending time in nature — which is often green? Plenty of research shows physical changes occur in our brains when we spend as little as 30 minutes in nature — even just going to a park.
Regardless, I’m excited about this field of exploration. While we may not have the keenest eyesight in the animal kingdom, we do seem to be uniquely evolved to engage with light and colors. And learning more about this relationship could open doors we can’t even imagine yet.
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