The impact of dietary protein on calcium absorption and kinetic measures of bone turnover in women.
Although high-protein diets induce hypercalciuria in humans, the source of the additional urinary calcium remains unclear. One hypothesis is that the high endogenous acid load of a high-protein diet is partially buffered by bone, leading to increased skeletal resorption and hypercalciuria. We used dual stable calcium isotopes to quantify the effect of a high-protein diet on calcium kinetics in women. The study consisted of 2 wk of a lead-in, well-balanced diet followed by 10 d of an experimental diet containing either moderate (1.0 g/kg) or high (2.1 g/kg) protein. Thirteen healthy women received both levels of protein in random order. Intestinal calcium absorption increased during the high-protein diet in comparison with the moderate (26.2 +/- 1.9% vs. 18.5 +/- 1.6%, P < 0.0001, mean +/- sem) as did urinary calcium (5.23 +/- 0.37 vs. 3.57 +/- 0.35 mmol/d, P < 0.0001, mean +/- sem). The high-protein diet caused a significant reduction in the fraction of urinary calcium of bone origin and a nonsignificant trend toward a reduction in the rate of bone turnover. There were no protein-induced effects on net bone balance. These data directly demonstrate that, at least in the short term, high-protein diets are not detrimental to bone.
Kerstetter
Jane E
JE
School of Allied Health, Box U-2101, 358 Mansfield Road, University of Connecticut, Storrs, Connecticut 06269-2101, USA. Jane.Kerstetter@uconn.edu
O'Brien
Kimberly O
KO
Caseria
Donna M
DM
Wall
Diane E
DE
Insogna
Karl L
KL
D000328:Adult; D001862:Bone Resorption / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D007700:Kinetics; D010012:Osteogenesis
D004044:Dietary Proteins; D002118:Calcium