Developing Biomarkers of Dietary Intake

Overview

Background: \- Researchers who study health and nutrition are interested in developing more accurate methods of determining what people eat from day to day and how it affects their general health. In particular, better methods are needed to determine if people are accurately remembering what they ate. One possible method involves the use of biomarkers, or indicators in urine, blood, saliva, fat, and hair, which are related to the intake of a particular food in a consistent way. One set of biomarkers in blood samples and hair may be used to determine the relative amount of meat, fish, and soda (corn/sugar cane) in a person s diet. However, more research is needed to study the effectiveness of using these biomarkers to accurately track dietary intake. Objectives: \- To validate the use of biomarkers as representative of specific dietary intake patterns (meat/fish/soda). Eligibility: \- Healthy, nondiabetic men between 18 and 65 years of age. Design: * This study involves an initial screening visit and a 12-13 week inpatient dietary study period. * Participants will be screened with a medical history and physical examination, as well as blood and urine samples and a glucose tolerance test to exclude individuals who have diabetes. * After 3 days of a standard weight-maintaining diet, participants will have a glucose tolerance test and a body fat scan; provide hair, blood, and fat tissue samples; and complete questionnaires and performance tests. * Participants will spend one day in a metabolic chamber to measure their energy expenditure and general metabolism. * Participants will then be randomized into one of eight carefully designed diets for 12 weeks. The diets will differ in the amount of meat, fish, and soda, including one diet where none of the three biomarker-related foods will be permitted. Blood samples will be collected throughout the study diet period. * At the end of the 12-week study diet period, participants will provide additional hair, blood, and fat tissue samples, and will have a second metabolism assessment in the metabolic chamber.

Studies of health and nutrition use a variety of tools to determine what people eat from day to day. Unfortunately, most of the methods used are not accurate for a variety of reasons and do not provide solid information on which to base health recommendations or public policy. In general, when people are asked to keep track of what they eat or recall what they have eaten in the past, they make mistakes in estimating both amounts and specifics of what was eaten. New tools that can help determine if people are accurately remembering what they ate are desperately needed. Biomarkers are things that can be measured (in urine, blood, hair, etc.) which are related to the intake of a particular food in a consistent way and may therefore be more accurate than a food record. One set of biomarkers that may be used are naturally occurring (present in all foods) stable isotopes of carbon and nitrogen to determine the relative amount of meat, fish, and soda (corn/sugar cane) in a person s diet. These isotopes can be measured in blood samples and hair. The aim of this study is to validate the use of stable isotope biomarkers as representative of specific dietary intake patterns (meat/fish/soda). This study will be an inpatient study in which highly specific diets will be fed to volunteers for \~12 weeks and stable isotopes will be measured in blood and hair. The ultimate goal is to develop biomarkers to be used to validate food intake patterns in outpatient clinical and epidemiological studies.