What cause most Vitamin D issues today is that people are NOT enough in the sun...
I personally dislike the sun and used to avoid it a lot (because I am more or less white and it burns me fast), now I have a really bad Vitamin D deficiency and was obliged by the medics to take supplements.
I stopped avoiding the sun... But it is still not really enough (I am programmer... I wake up in a dark room, walk to work in the sun, but the walk is 5 minutes, and then I stay indoors until night, when I walk back home, without any sun, thus my total sun daily is 5 minutes :/)