title: Dietary protein and skeletal health: a review of recent human research.
abstract: OBJECTIVE
  Both dietary calcium and vitamin D are undoubtedly beneficial to skeletal health. In contrast, despite intense investigation, the impact of dietary protein on calcium metabolism and bone balance remains controversial. A widely held view is that high intakes of animal protein result in increased bone resorption, reduced bone mineral density, and increased fractures because of its ability to generate a high fixed metabolic acid load. The purpose of this review is to present the recent or most important epidemiological and clinical trials in humans that evaluated dietary protein's impact on skeletal health.
  
  
  RESULTS
  Many epidemiological studies have found a significant positive relationship between protein intake and bone mass or density. Similarly, isotopic studies in humans have also demonstrated greater calcium retention and absorption by individuals consuming high-protein diets, particularly when the calcium content of the diet was limiting. High-protein intake may positively impact bone health by several mechanisms, including calcium absorption, stimulation of the secretion of insulin-like growth factor-1, and enhancement of lean body mass. The concept that an increase in dietary protein induces a large enough shift in systemic pH to increase osteoclastic bone resorption seems untenable.
  
  
  CONCLUSIONS
  Recent epidemiological, isotopic and meta-analysis studies suggest that dietary protein works synergistically with calcium to improve calcium retention and bone metabolism. The recommendation to intentionally restrict dietary protein to improve bone health is unwarranted, and potentially even dangerous to those individuals who consume inadequate protein.
authors.affiliation: Department of Allied Health Sciences, University of Connecticut, Storrs, Connecticut, USA. jane.kerstetter@uconn.edu
authors.forename: Jane E
authors.initials: JE
authors.lastname: Kerstetter
authors.forename: Anne M
authors.initials: AM
authors.lastname: Kenny
authors.forename: Karl L
authors.initials: KL
authors.lastname: Insogna
mesh_terms: D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004044:Dietary Proteins / Q000378:metabolism*; D006801:Humans
chemical_list: D004044:Dietary Proteins; D002118:Calcium