Project Number: 5450-51000-039-08
Project Type: Trust

Start Date: Oct 01, 2007
End Date: Dec 31, 2008

Objective:
This investigation will test the following hypotheses in a 15-wk controlled diet study of healthy postmenopausal women: 1. Dietary calcium is retained as well from a diet high in meat protein and potential acid load as it is from a diet low in meat protein and potential acid load. 2. Urinary acid and calcium excretion adapt over time (within weeks) to diets with high- or low-acid loads.

Approach:
General Approach - Twenty normal and healthy post-menopausal women will participate in the study. The volunteers will consume two diets, one low in protein (10% of energy), meat (20 g/d, 15 g/d as beef) and potential renal acid load (-17 mEg/d) and one high in protein (20% of energy), meat (74 g/d, 51 g/d as beef) and potential renal acid load (46 mEg/d). The diets will be consumed for 7 weeks each with a one week washout period (15 weeks total) in a randomized cross-over design. Both diets will contain approximately 700 mg calculated calcium to match the typical intakes of postmenopausal women. After 3 wk dietary equilibration (e.g., weeks 4 and 11), the entire 2-d menu of each diet will be radio-labeled with 47Ca. Calcium retention will be measured by whole body scintillation counting for 4 weeks after ingestion of the radio-labeled meals. Blood and urine samples will be collected to assess the effects of the diet on biomarkers of bone metabolism and renal adaptation to the acid-load. To screen for normal bone health, the bone mineral density, the volunteers will be measured by dual x-ray absorptiometry.