I've discussed this with my doctor after being severely low on vitamin D. It caused physical pain. I'm far enough north that it is impossible to get the sunlight needed during the winter. I still have days, but they are short without strong sun - not to mention that it is too cold to go without a jacket. So, supplements at least during the winter.
During the summer, I have the option of getting at least 15 minutes of sunlight a day (May through August). Being outside isn't enough: I need to make sure that more than just my face is exposed.
But then, on top of it all, I wound up taking a medicine that not only makes me sensitive to sun, but a bit more prone to a milder form of skin cancer. Sunscreen doesn't help with vitamin D production.
The end result is that I wind up taking vitamin D all year and simply get my levels checked from time to time. Luckily, the over-the-counter stuff does the trick (there isn't the variety in vitamins here as there is in the US).