I have no background at all in this but the link sent me down a rabbit hole of learning about myelin being comprised of carbohydrates and lipids.

Lipids have their own wikipedia page and apparently one of many ways to get lipids is vitamin D.

And of course carbohydrates seem to refer to sugars because the wikipedia article seems to say that myelin is made up of glucose.

But that only says what components you need, not what makes the body produce myelin.