Trouble is that to obtain enough vitamin D and at my age and this latitude ( northern NY state) is almost impossible. Even at any age. There are some studies that suggest a older person will not make use of the vitamin D rays as effectively as a younger one. There are differing conclusion by different experts on that question.
So, how do you get sun light when there is very little? You go to a sun parlor for your exposure. I recommend that you avoid high pressure lamps which are not similar to natural sunlight and avoid any exposure that causes reddening of the skin.
Reddening of the skin is damage and it is in the opinion of many what causes skin cancers. It should not be a surprise that some things are good in small doses and not so good in large doses.
So bottom line, cancer is less with vitamin D supplementation but all the indications are that sunlight maybe even more effective if you can get enough. Additionally they are seeing that remissions of symptoms occur more often when sunlight is part of the treatment with MS. No one knows exactly what component or effect causes this, but all we really need to know is that it works.
B Bennett CRNA Retired