CORRELATION OF DIET WITH THE ISOTOPIC COMPOSITION OF CARBON AND NITROGEN IN HUMAN KERATIN

Can a person's diet be correlated with the isotopic composition of carbon and nitrogen in human keratin (fingernails or toenails)? This study compares the isotopic composition of fingernails to diet. We collected fingernail samples from several dozen people from all over the country and world to analyze for carbon and nitrogen isotopic composition. We also collected information about each subject's diet by means of a survey. We measured the isotopic composition using continuous flow mass spectrometry in the Department of Geology at the University of South Florida. Isotope ratios are reported as ä13C and ä15N, measured with respect to reference materials. The carbon isotope ratios allow us to distinguish the relative proportions of C3 and C4 plants in the diet and determine trophic level. The nitrogen isotope ratios provide information about the contribution of fish, and other proteins derived from animals, and also discriminate between trophic levels of the subject. We are currently correlating diet and isotope ratios by comparing our mass spectrometry data with the dietary information provided by subjects. Based on dietary survey, we can distinguish between vegetarian/vegan and omnivorous diets, and the movement of immigrants from cultural regions characterized by significantly different average diets. Potential future applications of this study include diet problems and forensic analysis to identify distinguishing information regarding the diets of unidentified murder victims, with just the clipping of a fingernail.