CHEMICAL AND ELEMENTAL ANALYSIS OF HUMANS INVIVO USING IMPROVED BODY-COMPOSITION MODELS

Six chemical compartments [water, protein, mineral (osseus and cellular), glycogen, and fat] consisting of 11 elements (N, C, Ca, Na, Cl, K, H, P, O, S, and Mg) comprise greater-than-or-equal-to 99% of body weight in living humans. The combination of three neutron-activation systems, whole body K-40 counting, and (H2O)-H-3 dilution at Brookhaven National Laboratory now potentially makes it possible to quantify greater-than-or-equal-to 96% of the chemical and elemental determinants of body weight in vivo. The aims of the present study were 1) to develop 6- and 11-compartment chemical and elemental models, respectively, and 2) to evaluate these models in a group of 20 healthy adults. Results demonstrated that body weight estimated from either chemical or elemental components was highly correlated with (both r = 0.97, P < 0.001) and on average differed by < 4% from actual body weight. The compartmental results obtained using the chemical model were also evaluated by comparing calculated and actual body density (D(b)) estimated by under-water weighing. Calculated D(b) [1.041 +/- 0.017 (SD) g/ml] agreed closely and was highly correlated with actual D(b) (1.039 +/- 0.018 g/ml; r = 0.82; P < 0.001). Hence a near-complete chemical and elemental analysis of living human subjects is now possible and, with potential future refinements, represents an important opportunity to quantify the effects of gender, aging, and ethnic status on body composition.