Probably the most important of these is animal protein, which leaches calcium from the bones, leading to its excretion in the urine. A 1994 report in the American Journal of Clinical Nutrition showed that when volunteers are switched from a typical American diet to a diet eliminating animal proteins, calcium losses were reduced to less than half of baseline values. 9 Sodium, caffeine, tobacco, and a sedentary lifestyle also contribute to bone loss. High milk intake does not appear to be protective against fractures, even for whites. In fact, the fracture rates were slightly, but significantly, higher for those who consumed this much milk compared to those who drank little or no milk.
Many people prefer to get calcium from sources other than dairy products.
Many green vegetables have calcium absorption rates of over 50 percent, compared with about 32 percent for milk. In 1994, the American Journal of Clinical Nutrition reported calcium absorption to be 52.6 percent for broccoli, 63.8 percent for Brussels sprouts, 57.8 percent for mustard greens, and 51.6 percent for turnip greens. The fractional calcium absorption from kale is approximately 40 to 59 percent. Many Americans enjoy calcium-rich green leafy vegetables and beans, and preferences are not necessarily uniform across ethnic groups. In August 1997, the Opinion Research Corporation surveyed 1,000 adults for the Physicians Committee for Responsible Medicine, finding that preference for green leafy vegetables and beans were higher among African Americans than whites, and higher in the South than in other regions.