Many think that more calcium is better. Not so, in fact, there is increasing evidence that too much calcium is increasing the risk of heart disease and cancer. This is because there are different types of calcium and as I say often "it takes a little of a lot of substances to get a super hero team, not a lot of one thing " to get any job done. And that includes preventing and treating osteoporosis.I advocate to never take more calcium than magnesium and to never go without vitamins D and K-2.
Here is an article which goes into details about the link between calcium intake above 100 mg a day and breast cancer and heart attacks.
And how there is poor if not absent research for calcium supplements reducing fracture risk! I know you want to reduce your risk of breaking a bone and are taking calcium as a way to that end.
The article explains why vitamin K2 ingestion is crucial if you take vitamin D and calcium. And why food is the best source of calcium.
I agree with everything Dr. Mercola suggests here:
The bottom line is, optimize your vitamin D levels through sun exposure and consume a variety of fresh, local organic whole foods, including vegetables, fruits, nuts, seeds, organic meats and eggs, unprocessed salt, and raw organic unpasteurized dairy, which will give you the bioavailable calcium your body needs along with the trace minerals and other cofactors it needs to be absorbed and properly utilized by your body.
Avoid high doses of calcium and use a combination of food, sun exposure,exercise, good food (gluten free if you are gluten sensitive) and supplements including potassium, vitamin D, and K2 to prevent and treat osteoporosis.