There seems to be an ongoing controversy regarding the role of a diet high in animal protein and bone health. There have been several recent studies that elaborate on this topic. However, in sifting through the scientific literature, it is a well-established fact that protein does cause the body to lose calcium. One study in particular, the Harvard Nurses Health Study, found that those who consumed five or more servings of red meat per week had significantly increased fracture risk. Those who received their protein from plant sources had no increased risk. (Protein Consumption and Bone Fractures in Women, Feskanich et al. 1996, American Journal of Epidemiology, 143, 472).
The question is—does plant protein have the same bone-robbing effect as animal protein? Some studies, as the one mentioned above, show that plant protein does not increase the risk of fractures but there are contradictory studies on this subject. Some of the confusion and controversy about animal protein vs. plant protein and bone loss is partly due to the fact that the meat, milk, egg, and feed-crop production industries support many of these papers through grants. It is not surprising that the conclusion of papers sponsored by these self-serving industries contain biased opinions about the superiority of animal protein.
In reality, there are many ingredients that go into the making of healthy bones—not just protein. The alkalizing effects of a diet plentiful in fruits and vegetables offset the calcium-stealing effects of protein. To that end, vegetarians need to include in their diet foods rich in calcium and other essential minerals, make sure vitamin D levels are high, and there is increasing evidence that weight-bearing exercises are especially important in keeping bones healthy and strong.