Dietary Protein’s Impact on Skeletal Health
Both dietary calcium and vitamin D are undoubtedly bene„cial to skeletal health. In contrast, despite intense investigation, the impact of dietary protein on calcium metabolism and bone balance remains controversial. Further complicating this debate is the potential difference that animal and vegetable protein sources may have on skeletal health. One previously held view is that diets high in protein were considered to be detrimental to bone, because the inorganic acids generated from the metabolism of amino acids increase urinary calcium excretion. According to this hypothesis, continued loss of calcium in the urine eventually results in negative calcium balance and loss of calcium from skeletal stores, including osteopenia if systemic acidosis is chronic. An alternative hypothesis is that a higher intake of protein increases circulating levels of insulin-like growth factor-1 (IGF-1), increases intestinal calcium absorption and improves muscle strength and mass, all of which may potentially bene„t skeletal health.