ABSTRACT
This chapter introduces the theoretical concepts underlying the use of stable isotope ratios as dietary biomarkers. It provides a description of nomenclature and analytical methodologies, including considerations for sample handling and preparation. The chapter discusses how stable isotope ratios have been validated for use as dietary biomarkers, including free-living populations and controlled settings. Natural abundance stable isotope ratios have only recently attracted attention from nutritional epidemiologists for their potential as biomarkers of dietary intake. Isotope fractionation in the environment is the process that generates variability in stable isotope ratios among foods. Stable isotope ratios are measured using isotope ratio mass spectrometry (IRMS). Most nutrition epidemiology studies to date that have utilized stable isotope dietary biomarkers have measured the stable isotope ratio of the total sample carbon or nitrogen. The chapter describes potential applications of these biomarkers in an epidemiologic setting and provides examples of some early work demonstrating the utility of stable isotope dietary biomarkers to population-based studies.
