Let's be honest, most people aren't wearing sunglasses because they think it's healthy for them. Sunglasses are more of a fashion statement than anything these days. The question is, does blocking out certain frequencies of light have any negative effects on our health?
Let's start with a recent story of a case where sunglasses were introduced to an African tribe...
As the case mentions, this is just a correlation and obviously not a controlled study, but it should hopefully open your eyes (pun intended) to the rest of this article.
So, what do sunglasses actually do?
While sunglasses will vary in the type of light they block, most tints include an ultraviolet (UV) protection between 95-100%. UV light falls just outside the spectrum of 'visible light'.
What many people fail to realize is that just because you can't 'see' this type of light, it doesn't mean that your eyes can't detect it. In fact, studies have found specific UV receptors in the human eye (1).
So, why would UV light be bad for us if it is a component of natural sunlight AND we have receptors specifically dedicated to absorbing UV light?
I often wonder how we have been led to believe that we need to protect our eyes from natural sunlight, yet 95% of people do nothing to protect their eyes from artificial light on their PCs, cellphones, etc.
The role of UV light
UV light is well known to be the type of light that converts cholesterol to vitamin D in our skin, but what role does it play in our eye?
If you've ever heard of melatonin then you'd know it's more than just a sleep hormone. Melatonin is also one of the most powerful antioxidants in the human body. Research has even shown anti-cancer properties of melatonin (2).
It is often called the 'hormone of darkness' because the environmental cue for melatonin production is a lack of light (this is why artificial light at night damages your sleep quality). While this is true, it is only half of the story...
During the day we need UV light to convert tryptophan to the neurotransmitter seratonin (3). This builds up the stores for the mass production of seratonin to melatonin at night.
Can you see the link to the African tribe yet? Sunglasses = no UV light entering the eye = low serotonin production = low melatonin = increased cancer risk.
It should also be mentioned that low serotonin levels have also been shown to be associated with depression, anxiety, and carbohydrate cravings (4).
Unfortunately sunglasses do more than block out specific wavelengths of light. They also decrease the intensity of the light (measured in lux).
Seasonal affective disorder (SAD) is a type of depression which occurs in poor light cycles, primarily in winter. It affects between 1-10% of individuals, especially in areas furthest from the equator (5). The standard treatment for SAD is bright light therapy (6).
Light intensity is also the strongest factor in setting our circadian rhythm. When bright light hits our eyes it relays 'day-time!' to the brain. A lack of bright light during the day means your brain will never really get out of first gear, plus it won't have a reference for when it's time to unwind for sleep.
"The sun makes me squint"
Obviously you shouldn't be staring directly at the sun, but if you find yourself squinting even in morning light then you probably aren't getting outside enough. This would be like trying to run a marathon without doing any training.
If you're protecting your eyes from natural light, it's no wonder they're so sensitive when you actually go outside.
One of the best ways to acclimatize your eyes to sunlight is to get into more morning light.
This is when there will be the least UV light present and more of the longer wavelengths of light, i.e. the reds. This could be something as simple as enjoying your breakfast or morning coffee outside. You'll be surprised how quickly your eyes adjust to natural light.
If you want to learn more about light and how it affects us, be sure to subscribe to our email list below. You'll also receive The Complete Guide to Red Light Therapy in 2020 as a free bonus.