The interactions between 2h and 18 o natural abundance variations
and dlw measurements of energy expenditure.
Ritz, P., T. J. Cole, P. S. W. Davies, G. R. Goldberg, W. A. Coward.
Dunn Nutrition Centre, Medical Research Council, Downhams Lane,
Milton Rd, CB4 1XJ Cambridge, United Kingdom
APStracts 3:0066E, 1996.
Appropriate corrections for 2H and 18O natural abundance are necessary
in energy expenditure measurements with the doubly-labeled water
(DLW) method. The contribution of natural abundance variations to
errors in the method is generally ignored if an appropriate dose
level is given. Calculation of the appropriate dose level assumes
that 2H and 18O natural abundance are covariant and have a fixed
slope. This study has investigated the between- and within-subject
natural abundance variations, the latter over periods of time similar
to those used in DLW experiment. Although 2H and 18O natural
abundance are covariant between subjects, the slope of their
relationship is different from that of the Meteoric Water Line.
Within subjects there is no such a demonstrable covariance. It is
concluded that?: 1) the determinants of 2H and 18O natural abundance
are different within and between subjects; 2) the concept of an
optimal ratio of doses is not valid and a safer strategy is probably
to use a ratio greater than 10; 3) natural abundance variations may
contribute significantly to the magnitude of error in the DLW
measurements of energy expenditure.
Received 14 August 1995; accepted in final form 29 February 1996.
APS Manuscript Number E386-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 27 March 96