Purpose of review
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.
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.
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.