ASSESSING TOTAL-BODY PROTEIN, MINERAL, AND BONE-MINERAL CONTENT FROM TOTAL-BODY WATER AND BODY DENSITY

We hypothesized that investigators could assess bone mineral content ( BMC), total body mineral (M), and protein (P) from body water (W) and density (D-B) based on the theory of W. E. Siri (Advances in. Biologic al and Medical Physics, 1956, p. 239-280 and Techniques for Measuring Body Composition, 1961, p. 223-224) for body composition analysis. Sir i used one or more of the body components and the densities of the bod y, fat (F), W, M, and P to estimate one of the remaining fractional ma sses. We compared M, BMC, P, F, and fat-free mass (FFM) in 31 subjects (15 women and 16 men) computed from measurements of W and D-B with [4 -compartment (4C) model] and without [3-compartment (3C) model] BMC (f rom dual X-ray absorptiometry). 4C model P was calculated by differenc e (P = FFM - W - M). Mean difference (P > 0.05) ranged from 0.1 to 0.8 %. Correlations [+/-standard error of estimate (%)] between 4C and 3C model values were significant (r = 0.907 +/- 8.8, 0.907 +/- 8.7, 0.969 +/- 6.6, 0.998 +/- 2.0, and 0.999 +/- 0.7% for M, BMC, P, F, and FFM, respectively). We concluded that investigators can assess M, BMC, and P from W and D-B.