Yes but at the same time surprisingly short amounts of sunlight exposure can do already large effects.

Also some food contains vitamin D naturally.

So while food supplements can be necessary it depends on the rest of your diet and if you maybe could do a short brake during the time the sun is up (like a short outside cofe brake ;=))

EDIT: To be clear this is not meant to discredit you. It's just that even for people living high in the north there are options. Through for some less then for others.