In addition, if zinc is on the high side, and potassium is low, then taking extra magnesium will usually lower calcium, since magnesium supports zinc, but lowers potassium, which is a calcium synergist. On the other hand, if potassium is higher, and zinc is on the low side, then taking magnesium will likely push calcium higher as well. Vitamin D increases calcium, phosphorus, and - to a lesser degree - magnesium absorption... Full Text