Recent research from the British Medical Journal (article here), followed women for 19 years and compared calcium supplement dosages to rates of development of fractures. The results? Calcium supplementation maxes out its benefit around 750mg, with more not translating to better in terms of fracture rates.
Another piece of the women-calcium-fracture puzzle is that massively increasing calcium supplementation later in life (such as after an initial osteopenia or osteoporosis diagnosis) has minimal impact on bone density and fracture prevention by that point.
The last piece I can offer to this topic here is for interested readers to consult a Nutritionist or Naturopathic Doctor, as there are many dietary, supplementary and lifestyle variables to consider for one concerned about personal or family history of low bone density. Thank you for reading.