2012 Annual Report 1a.Objectives (from AD-416): Objective:. 1)Determine bone density;. 2)determine bone metabolism;. 3)evaluate calcium losses from the skeleton. 1b.Approach (from AD-416): Conduct a human study using 41Ca isotope tracer to quantify calcium losses directly from the skeleton in postmenopausal women. Sixteen healthy postmenopausal women will be enrolled and labeled with 41Ca tracer. Following tracer equilibration (~6mo.)women will be randomly assigned to 1 of 2 treatments:. 1)3-4 servings/d milk or. 2)equivalent calcium citrate supplementation. Following first intervention women will cross-over to the other intervention. Urine and sera samples will be collected and analyzed for 41Ca excretion, bone metabolism markers, PTH and 25-(OH)vitamin D. Documents Trust with Dairy Research Institute. Log 41795. 3.Progress Report: The goal of this agreement was to conduct a human intervention clinical study to examine the effect of calcium rich foods vs. supplements on bone metabolism in women. This project directly contributes to objective 1a of the in-house project. ARS scientists have enrolled 13 women in a dietary intervention protocol; 10 have completed the study to date. Urine samples from the first 10 enrolled participants have been processed for accelerator mass spectroscopy analysis for the 41Ca isotope. Samples from 6 women have been analyzed at Lawrence Livermore National Laboratory (LLNL). Urine samples for the remaining 4 women who have completed the project have been processed and are ready for analysis of the 41Ca isotope at LLNL. The next set of analysis have been planned for October 2012.