Breast Cancer and Calcium

When people say that breast cancer that has spread to the bones feeds off of calcium- does that mean that the calcium helps the breast cancer to grow? Or does it just break down the bone? My doctor told me I could continue to take my calcium supplement, even though I am on Zometa, because that little bit of calcium is not going to be too much and that I would probably need it, as I am also getting Zoladex shots, which she said will deplete my calcium eventually. But, if the calcium helps the cancer to grow, I am afraid to take it. Is this the case? Does calcium actually promote cancer growth?

[CCF-RN,MSN-rf]

Dear Chellesk:  Calcium does not promote cancer growth.  The concern around calcium has to do with bone damage.  Simplified, as the cancer destroys bone, calcium is released into the bloodstream.  The more bone damage, the higher the calcium may rise.  Our blood normally has calcium in it.  The problem is that too much calcium in our blood can be harmful.  Symptoms of too much calcium (hypercalcemia) can include some of the following, frequent urination, excessive thirst, dehydration, fatigue and profound muscle weakness, nausea, vomiting, constipation, itching, and confusion.  The diagnosis is made by drawing a blood calcium level.  This is a treatable condition but it can be quite serious.  So, in people with a lot of bone damage, taking extra calcium may not be recommended.  However, if your calcium levels are normal and you are on medication that depletes calcium, then a supplement may be just fine as your doctor suggested.  Periodically, he is probably already checking your calcium levels, among other things.