So take Magnesium and D together?
absolutely on the Magnesium. Due to our diets being primary processed wheat, sugar, oil, and animals, (and partially due to soil mineral depletion) our diet is persistently low on Magnesium by quite a large margin. the impact of this on the population is not consistent. this really doesn't get enough attention in the media or many other places.
Magnesium is very important cofactor for metabolism of Vitamin D (and many other things, it’s a cofactor involved with hundreds of enzymes and such), which people are also generally low on.
I think there may be another big cofactor or two, but they escape my offhand recollection.