Seattle, where I went to naturopathic school, has a climate fairly similar to Scotland, with similarly low levels of sunlight throughout much of the year, and with similarly high incidence of MS. In my time there, I don't know if I saw one patient with a healthy blood level of vitamin D who wasn't actively supplementing it. In fact, researchers believe that most Americans aren't able to make adequate vitamin D throughout much of the year, due to weather, indoor lifestyles, and seasonal changes in the angle of the sun's rays to the earth below.
The good news is - vitamin D is inexpensive and effective at raising blood levels. It's an easy test with an easy fix, and the health benefits are significant. So the question is, do you know your vitamin D levels?