A diet high in meat protein and potential renal acid load increases absorption and urinary excretion of calcium, as well as serum IGF‐I in postmenopausal women

Abstract

The objective was to determine the effect of increasing protein and potential renal acid load (PRAL) on Ca retention and markers of bone metabolism.In a randomized crossover design, twenty postmenopausal women consumed two diets: one low protein, low PRAL (LPLP) and one high protein (mostly meat), high PRAL (HPHP) for 7 wk each, separated by a one‐week break. After 3 wk, the entire 2‐d menu of each diet was radio‐labeled with 47Ca and retention was measured by whole body scintillation counting for 4 weeks. Biomarkers of bone metabolism in blood and urine were measured.ResultsCompared with the LPLP diet, the HPHP diet increased urinary acidity (pH: 7.1 vs. 5.9, ±0.25*, p < 0.01), urinary Ca excretion (156 vs. 203, ±63 mg/d, p < 0.01), and blood IGF‐I levels** [137 (103 ‐ 184) vs. 174 (130 ‐ 232) ng/ml, p < 0.01) consistently from week 1 through 7. The fractional Ca absorption was lower in subjects with LPLP than with HPHP diet (25.0 vs. 30.4, ±5.4%, respectively, p < 0.02). The HPHP diet tended to increase the absolute amount of Ca absorbed compared with LPLP diet (227 vs. 258, ±47 mg/d, p < 0.08).ConclusionsIn postmenopausal women, a diet high in both meat protein and PRAL increased serum IGF‐I and Ca absorption, which compensated the increase in urinary excretion. A high meat diet does not appear detrimental for bone health.*Pooled SD; **Geometric means (range).Supported by USDA‐ARS and the National Cattlemen's Beef Association.