How to get enough Vitamin D by sun exposure? Part 1

1 June 2021

What is UVB light?

We’ve been talking a lot about UVB, and you may also hear about it when reading about Vitamin D production from sunlight. But what is UVB? UVB (ultraviolet B) is a specific type of ultraviolet radiation present in the sun rays, and it is needed for your skin to produce Vitamin D. UVB is a relatively high energy radiation (compared to visible light, which spans the light spectrum from violet/blue to red) as shown in the figure 1 below.

As a consequence UVB is a radiation with a shorter wavelength (which is in the range 280–315 nm) than any of the visible light, as you can see on the left side of the violet/blue light, and it is invisible to the human eye. In the figure below, you can see the visible spectrum squeezed between ultraviolet (UV) radiations, and infrared radiations (IR).

Fig. 1: The visible light spectrum. Reproduced from http://www.illinoislighting.org/lightcolor.html

An important point to notice is that UVB is not always present in the sunlight that reaches us, because it strongly depends on several factors, such as the season, the time of day, and your geographical location. The amount UVB present during the day varies all year long, as does its strength which is often measured by the UV index (UVI)! More to come on this topic in the next post…

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