ENERGY EXPENDITURE USING DOUBLY LABELLED WATER
Iso-Analytical provides a full range of
analytical services for customers wishing to determine Energy Expenditure using doubly
labelled water. The Doubly Labelled Water (DLW) method uses the natural occurring
stable isotopes of water (D2O and H218O) to assess energy expenditure, body composition
and water flux in humans and animals. The DLW method is entirely safe and
non-restrictive, requires only periodic sampling of body fluids and is well suited
for measurement of energy expenditure in free-living or hospitalized patients.
The basis of the DLW method is to follow the decline in enrichment of the stable
isotopes of oxygen (oxygen-18, 18O) and hydrogen (deuterium, 2H) in body water after initial
labeling of the body water pool. As oxygen-18 is lost from the body in the form of water
and carbon dioxide (CO2), whereas deuterium is lost only as water, the difference in loss from the body reflects
the CO2 production during the period. Because CO2 production is the result of fat,
carbohydrate and protein oxidation, it is an index of energy expenditure.
We are able to undertake analyses on samples of urine, blood or saliva,
although urine is most commonly used because of ease of collection from subjects.
Following collection and prior to analysis samples (approx. 5 mL for urine)
should be stored in plastic containers at -20 °C.
We will equilibrate the
body fluid samples under controlled conditions with hydrogen for 2H analysis
and carbon dioxide for 18O analysis. All determinations of isotope enrichment
will be made using Europa 20-20 continuous-flow isotope ratio mass spectrometers.
View Example Laboratory Report for DLW analysis for Total Body Water composition.
Please contact us for further information of use our
quote form to obtain a costing.
Doubly Labelled Water:
Theory and Practice By John R. Speakman (ISBN 0412637804)
Measuring Physical Activity and Energy Expenditure By Henry Joseph Montoye (ISBN 0873225007)