Whether higher protein diets protect bone health and promote calcium retention when healthy, physically active adults routinely undergo periods of increased metabolic demand has been of particular interest to our laboratory. Using a nonobese animal model, we demonstrated that long-term consumption of MPC and soybased higher protein (32% total energy intake), adequate-calcium diets suppressed parathyroid hormone secretion, attenuated bone turnover, and increased trabecular volumetric bone mineral density independent of energy status and, in large part, protein source. In a well-controlled human study, where volunteers consumed about 1000 mg calcium per day, we investigated whether systematic increases in dietary protein above the RDA (2 and 3 times) resulted in progressive increases in calcium absorption and improvements in biomarkers of bone turnover in healthy, physically active adults during short-term periods of weight maintenance (10 d) and weight loss. We found that dietary protein had neither an effect on calcium absorption nor did increased protein intake augment net calcium retention and biomarkers of bone turnover. These findings were unexpected and likely due to the small differences in PRAL between protein groups, suggesting the calciuretic effect of dietary protein is largely attributed to its metabolic acidity or its contribution to dietary PRAL rather than protein, as such. Assuming calcium intake is consistent with the RDA (1000 mg/d), our data suggest that healthy, physically active adults can consume protein at levels up to 3 times the RDA without disrupting calcium homeostasis and bone integrity during weight maintenance and weight loss.