Using biomarkers to assess the accuracy of dietary assessment methodologies.

摘要

Research in nutritional epidemiology seeks to understand relationships between diet and disease. Error in dietary assessment can lead to an underestimation of disease risk or false conclusions regarding diet and disease relationships. Improving the accuracy of dietary methodologies for capture of habitual dietary intake in large study populations can increase the understanding and interpretation of results from epidemiological studies.; An extensive review of studies where dietary intake was determined by self-report while energy expenditure was measured simultaneously by doubly labeled water (DLW) demonstrated a potential for reporting error. Among 23 studies evaluated, energy intake was under reported on average by 20%, but all studies involved small, select populations.; To test dietary instruments in a large, general population, we collaborated with the National Cancer Institute on the Observing Protein and Energy Nutrition (OPEN) study. This study used DLW and urinary nitrogen as biomarkers to examine bias in the reporting of total energy and protein intake. Energy intake was under reported in this study by 16 ± 6% on the diet recall and by 35 ± 5% on the diet history questionnaire.; The validity of a single measurement of energy expenditure as representative of an individual's average expenditure has been questioned. To study the reliability of DLW measurements, a repeat measurement was obtained in a subset of OPEN participants. The coefficient of variation of the DLW energy expenditure method was 5.1% demonstrating that it is a precise measure of energy expenditure.; The under reporting of energy intake on dietary surveys could result from either generalized portion size errors or the underreporting of specific foods. To distinguish between these sources of error, the accuracy of reported meat intake was assessed using a biomarker of meat intake, urinary 3-methylhistidine (3-MH). Compared to accurate reporters of energy intake, under-reporters misreported their true meat intake resulting in a weakened association between reported intake and urinary 3-MH excretion. Moreover, under-reporters of energy intake under reported meat intake in proportion to their under-reporting of calorie intake. This finding supports the use of energy adjusted intake values in studies exploring the relationship between meat intake and disease.