Vitamin D, Windows, and The Sun: A Dermatologist's Perspective

Wondering if that sunny spot by your office window is giving you all the vitamin D you need? Dr. Stefanie tackles this common misconception head-on with scientific clarity.

The truth might surprise you: despite feeling the sun's warmth through glass, your body isn't getting the specific ultraviolet rays needed for vitamin D production. This episode breaks down the crucial difference between UVA rays (which can penetrate glass and age your skin) and UVB rays (which are blocked by windows but essential for vitamin D synthesis).

Transcript

Introduction to Dermatologist Debriefs

Speaker 1 0:01

Dermatologist debriefs . Join no-nonsense dermatologist Dr Stephanie Williams as she debunks myths and shares her professional insights , separating facts from fiction , in just a few minutes .

Patient Question About Vitamin D

Speaker 2 0:17

Hello , this is Dr Stephanie . I was just asked by one of my patients whether they really have to take their vitamin D supplement now that it's starting to get sunnier outside . This patient has an office job and spends most of her day inside , but she argued that her office is very bright and she sits right by the window where there is a lot of sun coming in . So today's question is can our skin produce enough vitamin D when sitting behind a window

Can Windows Provide Vitamin D?

Speaker 2 0:52

on a sunny day ? And the answer to that is no , and this is because the action spectrum of vitamin D production lies in the UVB range . Production lies in the UVB range , and

UVB vs UVA Wavelengths Explained

Speaker 2 1:12

UVB does not penetrate glass windows . So if we look at this in a little bit more detail , we all know that vitamin D production requires ultraviolet rays from sunlight , and vitamin D production is most efficient when the sun is at its highest point in the sky , which is around midday , and , of course , the larger the area of skin exposed , the more vitamin D is produced . However , it's UVB , specifically from the ultraviolet range , that is required for vitamin D production .

Speaker 2 1:41

For vitamin D production , uvb includes wavelengths from 280 to 320 nanometers , which is compared to UVA , the higher energy portion of the sunlight , which can cause our skin to burn . However , although the UVB range compared to UVA has higher energy , uvb is relatively easily blocked or at least reduced , let's say , for example , by clouds or by clothing or even normal window glass .

Alternative Vitamin D Sources

Speaker 2 2:18

So this is in contrast to UVA , which has longer wavelengths , namely 320 to 400 nanometers . But UVA can penetrate not only much deeper into the skin but also has a much better ability to penetrate things like clouds and window glass , and that's why , when you're sitting inside behind a window , you will generally not burn . But your skin can still age prematurely and you can see that , for example , in professionals who drive , for example , lorry drivers or taxi drivers , taxi drivers and if you compare their hands and forearms , you can see that generally the side that is closer to the window is looking more prematurely aged than the other side .

Speaker 2 3:20

So , to cut a long story short , uva can window glass , but it is not useful for our skin with regards to vitamin D production . So this action spectrum lies firmly in the UVB range and that does not penetrate window glass . And , on that note , if we're wearing sunscreen , which also greatly reduces the UVB getting into the skin , that of course then also limits our vitamin D production in the skin . So what are the alternative sources ? That's , of course , besides sunlight supplements , which I highly recommend taking . Some foods also contain a certain degree of vitamin d , like fatty fish or egg yolks , but it's not generally enough . So either you expose your skin directly to the sunlight outdoors , which obviously comes with its downsides , or you start taking a supplement . I hope this makes sense and I will speak to you very soon .