Adequate calcium intake may not prevent the accelerated bone loss in women during and for several years after menopause, caused by estrogen deficiency. Environmental factors are believed to have more influence on the rate of bone loss in later life. Steroid medications decrease calcium absorption. People with rheumatoid arthritis, inflammatory bowel disease and asthma often need to be treated with these medications for long periods of time, leading to higher risk of fractures. Some foods high in calcium also contain oxalic acid, which interferes with calcium absorption.
Spinach is such a food.
Most adult men and women fall short of optimal recommended calcium intake. If you choose to take supplements, LaCroix suggests checking the number of milligrams of calcium in each pill and calculating how much you need in addition to dietary sources to reach the recommended level for you. Taking calcium supplements with meals ensures the best absorption, because more gastric acid is present for digestion. If it dissolves in several minutes, it will be readily absorbed. You'll be better able to retain the bones that you have today, and reduce your risk of breaking those bones in the future.