While calcium and dairy can lower the risk of osteoporosis and colon cancer, high intake can increase the risk of prostate cancer and possibly ovarian cancer.
Plus, dairy products can be high in saturated fat as well as retinol (vitamin A), which at high levels can paradoxically weaken bones.
Good, non-dairy sources of calcium include collards, bok choy, fortified soy milk, baked beans, and supplements that contain both calcium and vitamin D (a better choice than taking calcium alone).