Nutrient Validation In Women's Lifestyle Validation Study

Nutritional factors have been intensively studied as important determinants of many diseases. Food frequency questionnaires (FFQ), dietary records, 24-hour dietary recalls, nutrient biomarkers are important dietary assessment methods, and are subject to various sources of measurement error. Given the limitations of these methods, much effort has been devoted to refining them and evaluating their ability to measure diet. This dissertation focused on evaluating the performance of a semi-quantitative FFQ (SFFQ), multiple web-based automated-self-administered 24-hour recalls (ASA24), 7-day dietary records (7DDR) and biochemical indicators in assessing nutrient intakes among women. Intraclass correlation coefficient, Spearman correlation coefficient, and validity coefficient calculated by method of triads were used to evaluate the reproducibility and validity of each dietary method. The first paper evaluated the performance of a 152-item SFFQ comparing intakes of nutrients estimated by SFFQ with those measured by the average of two 7DDR, and of four ASA24s kept over a one-year period. The study SFFQ performed consistently well when compared with multiple diet records, and that modifications to the questionnaire over time have adequately taken into account the changes in the food supply and eating patterns that have occurred since 1980. Multiple ASA24s can provide similar estimates of validity as dietary records if day-to-day variation is taken into account. The second paper explored the validity of long-term intakes of energy, protein, sodium and potassium assessed by SFFQ and ASA24s using recovery biomarkers and 7DDR as standards. The study SFFQ and averaged ASA24’s are reasonably valid measurements for energy-adjusted protein, sodium and potassium compared to multiple recovery biomarkers or dietary records. Recovery biomarkers should not be considered to be without error, including systematic within-person error. Finally, the third paper further evaluated the validity of nutrient assessed by SFFQ and ASA24 compared with intakes by the 7DDR and plasma levels of fatty acids, carotenoids, retinol, tocopherols and folate. Again, the study SFFQ provides reasonably valid measurements for specific fatty acid, most carotenoids, alpha-tocopherol and folate compared to concentration biomarkers or dietary records. Compared to SFFQ, almost all nutrients estimated by averaged ASA24s had relatively low correlations with biomarkers, 7DDRs and estimated ‘true’ underlying intakes.Nutritio