With advancing age, our bodies experience an inexorable loss of bone. Two major studies in elderly populations now underscore the importance of dietary protein in this structural erosion, which can lead to osteoporosis. The reports come to sharply different conclusions, however, about the effect of animal protein on the rate of bone loss.
In one study, diets rich in animal protein correlated with greater bone loss and fracture risk. In the other, animal protein appeared to protect bone.
Such contradictions, "which are not very satisfying," often emerge from observational studies where researchers record the natural habits and health of people, notes Robert P. Heaney of Creighton University Medical Center in Omaha, Neb. "That's not a criticism of such studies," he says, just a reminder of the uncontrollable variables rife in populations.