To the Editor.
—Although Dr Klesges and colleagues1 carefully assessed standardization and quality control of the dualenergy x-ray absorptiometry (DEXA) equipment used for the estimation of BMC and body composition, there is reasonable doubt that the changes in BMC they described are valid findings. It seems to be a treacherous coincidence that body calcium excretion with or without calcium supplementation impacts directly on the bone mineral status for the following reasons.All DEXA inherently uses 2 radiation energies to resolve equations comprising at least 3 unknown variables: the attenuation coefficients of fat, water, and bone mineral. Fat and water have considerably different attenuation coefficients at low energies. In common experimental settings, such as crosscalibration efforts with invariable anthropomorphic phantoms, certain systematic errors are not detectable.2 The influence of fat distribution on bone mass measurements with DEXA can be of considerable magnitude and ranges up toInfluence of simulated nonhomogeneous fat and
Schneider P, Reiners C. Changes in Bone Mineral Density in Male Athletes. JAMA. 1997;277(1):23-24. doi:10.1001/jama.1997.03540250031025