I don't have the source handy but there was a geographic point made about Scandinavia that went something like this:

- Scandinavia is very far north and therefore gets less sun in the winter (obviously)

- Apparently the soil of Scandinavia is well suited to crops that are high in Vitamin D

The soil being good for Vitamin D crops (plus lightening of skin/hair and fish diets etc) was a part of why people were able to live in such far northern climates even if they didn't always have access to fish.