I have a love/hate relationship with Vitamin D. It keeps my immune system in pretty good order. When taking it (5000 IU every third day) I never seem to get sick. But, it also seems to worsen my constipation. After laying off of it for a while recently I decided to start back. After taking for 4 days solid I got horribly constipated. Now I've heard in the past that D3 needs magnesium as a cofactor, but I don't recall seeing a ratio or a suggestion of which type of mag is the best. I'm just wondering if D3 along is depleting my mag stores, thus causing constipation.