“According to the NIH, at the latitude of Boston you will make no vitamin D from sunlight for the four months of Nov. through Feb. If that’s so then you will make little vitamin D from sunlight for much of the rest of the year.”
I’m in the PA area, but since I get little natural sunlight,
I supplement.
Is that Pennsylvania? Not much further south than Boston.
And it doesn't much matter. According to the NIH, it's somewhere in S. Carolina where you can make D from sunlight year round. But how much? Think about it and even in the southern states it must be a good part of the year when you couldn't make much D from sunlight no matter how much time you spent outdoors. Maybe in southern Florida.