Vitamin D deficiency & heart disease

Vitamin D: New way to treat heart failure?. It's been in the news so I figured I'd point to Think Gene's roundup. It seems in the health sciences occasional fads for miracle-nutrients show up, so take it all with a grain of salt. I'm less interested in Vitamin D's relationship with late in life ailments such as cancer and heart disease as I am with its more global impact on immune function, because it is the latter which has the most evolutionary impact (most people done breeding by the time heart attacks and cancer take their toll).