Vitamin D and the UV spectrum:
the sunshine hormone

Vitamin D carries a small lie in its name. It is not just a vitamin we get from food — it is a prohormone that the body largely makes itself, using sunlight. More precisely, using one narrow part of the spectrum: UVB.

Receptors for vitamin D are found in cells throughout the body — in bones, immune cells, muscles and even the brain. That hints at how broad the influence of this "sunshine hormone" is. Vitamin D deficiency is extremely common at our latitudes, especially in winter and among people who work indoors.

How the skin makes vitamin D

The skin contains a molecule derived from cholesterol (7-dehydrocholesterol). When UVB radiation (roughly 280–315 nm) lands on it, it converts into a precursor of vitamin D. The body then processes this further in the liver and kidneys into the active form. The whole process is triggered solely by UVB — not heat, not visible light, not UVA.

Why nothing forms in winter or behind glass

Here's the catch. UVB is short-wave and easily blocked. The consequences are twofold:

• Winter months — with the sun low, so little UVB passes through the atmosphere that vitamin D production is practically zero for several months across most of Europe.
• Window glass — ordinary glass blocks almost 100% of UVB. The sun behind a window warms you pleasantly (that is infrared and visible light), but it makes no vitamin D.

So even a whole day by a sunlit window doesn't solve the problem. The body gets warmth and brightness, but not the very wavelength it needs for vitamin D.

A controlled UV component — with respect

Ultraviolet light is a double-edged sword. In small, controlled amounts it triggers vitamin D production and has its place. In excess it damages the skin and raises risks. That is why moderation and protection are essential with any device that has a UV component.

With the HELIOR One panel this means clear rules: use the UV component only briefly — a maximum of 3 minutes per session — and always with the protective goggles included in the box. Thanks to the independent channels, UV is fully separated from the Red and NIR spectrum, so you switch it on only when and as much as you actually want. The panel is not a tanning bed and is not intended for tanning.

Light, supplement, or both?

Many people address vitamin D deficiency with oral supplements, and it is a practical route, especially in winter. Natural production from UVB, however, has further nuances that science is still studying. Which route suits you — and at what doses — is best discussed with a doctor, ideally based on a measured blood level of vitamin D.