Filtered Sunlight

I was sat at the window seat, on a sunny day, at a cafe typing away on my computer like I usually do. After all, whats work without a little people watching eh? Besides, I figured, it was a win-win. I'm working and getting some Vitamin D from the sun rays hitting my skin at the same time. As a bonus, since I was indoors, it was warm too. So, even though it's autumn and mild, it felt like summer. What's not to love?

In usual fashion, I've learnt to question my assumptions all the time. I wondered if that was actually true, the Vitamin D thing, and decided to look into it. I was aghast at what I found actually. It turns out that I've been deriving near-zero benefit from sitting by the window when it comes to Vitamin D. If anything, I've been harming myself somewhat. WHAT!?

Like we all know, or if you didn't know, now you know, the sun rays trigger the synthesis of Vitamin D in our bodies. Our kidneys and livers then work together to transform the Vitamin D into biologically active versions our bodies can use in our immune system, bone health and general body maintenance. Super important stuff.

So, what's the issue? The sun can go through glass, glass being transparent and all, and I can feel the warmth of the sun on my skin. Why am I not making an Vitamin D when sat at the cafe window?

What actually triggers the Vitamin D synthesis are the ultraviolet (UV) rays of the sun, not the entire light spectrum. There are also two types of UV; UVA and UVB. UVB is the specific one responsible for triggering the production of Vitamin D. UVA, on the other hand, is pretty harmful if we're exposed to it for too long, or in high doses. They can penetrate deep into the skin and cause premature ageing.

The mechanisms via which the cause the ageing are multiple. UVA can encourage the production of "free radicals" which increase "oxidisation" in our body. It's basically rust. We rust, like anything else on earth, when exposed to oxygen ions. This is beyond the scope of this post, so maybe I'll dedicate an entire post to how oxygen kills us slowly. The wavelength of UV light is also small enough to splice DNA which can lead to genetic mutations and cancer. This is one of the mechanisms responsible for skin cancer caused by sun exposure.

This is the problem. Most commercial glass used to make windows and windscreens, like sun glasses, block UVB rays, but not UVA! You have to look for glass that specifically blocks UVA if you want that protection. Effectively, sitting at a cafe window on a sunny day, one is exposed to UVA but no UVB! So the good stuff has been filtered out of the rays, and the bad stuff isn't. How crazy is that?

The one saving grace, in my case, is that I have a high level of epithelial melanin - aka, dark skin. Melanin is our protection from UVA, and to an extent UVB, radiation damage. Everyone has melanin, even the lightest skinned people, but in different concentrations. Melanin in people of my complexion can absorb 100% of UVA under normal exposure. Prolonged exposure can case a little damage, as I've once experienced in Senegal after playing basketball shirtless for 5 hours in the blazing 45 degree sunlight. I, believe it or not, was sunburnt - with the irritable peeling skin and everything haha. Now I have empathy for some of you 😅

Ironically, it's this same high melanin content that prevents me from attaining enough UVB in temperate weathers like in the UK, causing me to have to try exposing myself more in the first place. Thank goodness for Vitamin D supplements. The bottom line is, sitting at the window and "sunbathing" through glass, isn't that good for you. You have to actually go outside!

Peace & Love,

Adé