Body & HealthFact
Your body makes a vitamin from sunlight and cholesterol.
When UV-B hits skin, it converts a cholesterol precursor into vitamin D3; liver and kidney activate it. The vitamin controls calcium uptake for bones. In Germany, UV-B from October to March isn't enough – the sun sits too low. The RKI estimates around 30 % of adults are under-supplied.
Useful: In Central European winters, vitamin D is stock left over from summer.
Source: en.wikipedia.org