• Developing Stable Isotope Biomarkers Of Yup'ik Traditional And Market Foods To Detect Associations With Chronic Disease Risk

      Nash, Sarah H.; O'Brien, Diane; Bersamin, Andrea; Boher, Bert; Kristal, Alan (2013)
      This dissertation addresses the need for valid measures of dietary intake for use in studies of chronic disease risk in the Yup'ik population of Southwest Alaska. The Yup'ik people have experienced dietary changes over the past century, as consumption of traditional foods has been increasingly supplemented or replaced by market-purchased foods. Determining whether this dietary change is associated with increases in chronic disease risk is important for making nutritional recommendations for disease prevention. However, monitoring dietary change is challenging, in part due to the limitations of self-reported methods of dietary assessment. Dietary biomarkers are promising alternatives to self-reported methods, because they can provide unbiased, reliable estimates of intake. In this dissertation, I present evidence towards the validation of stable isotope dietary biomarkers. Stable isotope ratios vary among foods that are important in Yup'ik diets, and are incorporated into tissues, including several commonly collected biological sample types. They are simple, inexpensive and reliable measures that would be powerful tools for dietary assessment if they could be validated as biomarkers of certain foods. This work was conducted with two Yup'ik study populations that participated in studies conducted by the Center for Alaska Native Health Research. I begin by showing that the nitrogen isotope ratio is a marker of the marine component of traditional food intake, and the carbon isotope ratio is a marker of market food intake. I then calibrate a model of sugar intake based on both the carbon and nitrogen isotope ratios. I focus specifically on sugars because intake of sugary foods and beverages has been linked to obesity-related disease risk in other US populations. Finally, I use this dual isotope model to assess associations of sugar intake with chronic disease risk factors. I find that sugar intake is associated with blood pressure, blood lipids, leptin and adiponectin, suggesting a potential adverse effect of sugar intake on Yup'ik health. The findings of this dissertation provide substantial evidence to support carbon and nitrogen isotope ratios as markers of Yup'ik dietary intake, and demonstrate their potential to be informative in studies of associations between dietary intake and the health of Yup'ik people.