Dr Oz says to take Magnesium

Response to the last writer - magnesium doesn't promote calcium absorption.  The pro-hormone known as Vitamin D does. Magnesium is not the wonder drug as here noted. Magnesium has been used for a long time to promote the transport of water into the colon ...anyone heard of "Milk of Magnesia" ???

Magnesium isn't needed for calcium absorption, but vitamin D is!  Calcium and magnesium often come together in the same formula because calcium may be binding for some and magnesium has a laxative effect. It's more important to take calcium and vitamin D together for best calcium absorption though. There are different forms of vitamin D, as well as different form of calcium and magnesium. Look for vitamin D3 (its also called cholecalciferol) vs vitamin D2 (which is also called ergocalciferol). D3 is better absorbed. There are different forms of calcium too..calcium carbonate (Viactiv, Tums, etc.  The ones that have ~500mg per dose).  This form can cause more gastrointestinal  upset (and should therefore be taken with food)  than calcium citrate (Citrical). Calcium citrate can be taken on an empty stomach and may cause less stomach problems, but the downside of calcium citrate is that you usually have to take more pills...it might take 2-3 tablets to give you 500mg calcium.