In much of Scandinavia, for a stretch of every winter, the sun sits too low in the sky for skin to make much, if any, vitamin D. It is not about cloud cover or staying indoors. Above a certain latitude, the angle of the sunlight itself is wrong for months at a time. This single fact explains why Nordic public health has treated vitamin D as a matter of routine for generations — why cod liver oil was spooned out to children, and why supplementation through the dark season is standard advice rather than a fad.
So the Nordic case is easy. The interesting part is everyone else.
The vitamin your skin makes, until it can't
Vitamin D is unusual among nutrients: your body manufactures most of it when UVB light hits your skin. Food contributes some — oily fish, egg yolk, fortified products — but sunlight normally does the heavy lifting. That is exactly why it becomes a problem in the North, where the sunlight simply switches off for part of the year.
Norwegian and other Nordic health authorities respond to this with clear seasonal guidance, and it is one of the few areas of nutrition where the advice is genuinely settled rather than contested.
Why sunny countries are not exempt
Here is the counterintuitive turn, and the reason this is not only a Nordic story.
Low vitamin D status also occurs in sunny regions, including parts of the Middle East and South Asia. The reasons are ordinary rather than exotic: people may spend the hottest hours indoors or in shade, clothing and sun protection reduce UVB exposure, and melanin reduces the rate of vitamin D production in skin. Latitude is only one part of the picture.
Add it up and you get a genuinely global picture. It is not simply "cold places lack sun." It is "modern life, in many climates, keeps skin away from midday light" — and the body cannot tell the difference between a Norwegian December and an air-conditioned office in a hot country.
The balanced way to think about it
We are not going to tell you that you personally are deficient, because a blood test is how vitamin D status is assessed, and that is the honest answer. What we will say is that vitamin D is one of the few nutrients where "just get more sun" is not a universal fix — for the North because the sun leaves, and for much of the rest of the world because daily life quietly gets in the way.
The Nordic habit of taking it seriously through winter is worth borrowing. But the reason to pay attention is not your latitude. It is how much of your actual day your skin spends in real daylight — a question that turns out to have surprising answers in Bergen and Bangalore alike.
Sources and further reading
This article is educational and is not medical advice.
