Validation of dietary data in pregnancy : Validation of the food frequency questionnaire developed for the Norwegian Mother and Child Cohort Study (MoBa)
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AbstractDue to recent insight into the relation between fetal nutrition and health of the child both early and later in life, assessment of maternal diet has become an integral part of pregnancy and birth cohort studies. A new food frequency questionnaire (FFQ) was developed for monitoring maternal diet in the Norwegian Mother and Child Cohort Study (MoBa). The basis for this thesis in nutritional epidemiology was to assess the relative validity of the new FFQ. A validation study was carried out with 119 women in MoBa. Reference measures were a 4-day weighed food diary (FD), a motion sensor for measuring total energy expenditure, and diet-related biological markers in urine and blood. The dissertation contains five scientific papers. One presents the main methodological challenges when developing a new instrument for monitoring dietary intake in pregnant women. The other papers report on the validity of different foods and nutrients measured by the new FFQ relative to the reference measures. The average correlation coefficient between the FFQ and FD was 0.48 for foods and 0.36 for nutrients which is accepted as an overall good agreement. Urinary recovery biomarkers and serum/plasma concentration biomarkers confirmed that the FFQ was able to distinguish between high and low intake of nutrients and foods. Furthermore, the biomarkers examined in the validation study confirmed differences in self-reported micronutrient intake between supplement and non-supplement users for vitamin D, beta-carotene, folate, n-3 fatty acids, flavonoids and iodine, showing that self-reporting is valid for classification of pregnant women according to dietary supplement. Results from the validation study confirmed the applicability of biomarkers in the validation of dietary data in pregnant women. In conclusion, the results demonstrate that the MoBa FFQ provides valid intake estimates and is able to rank pregnant women according to dietary intake of foods and nutrients.
Meltzer HM, Brantsæter AL, Alexander J, Ydersbond TA, Haugen M and the MoBa Dietary Support Group. Methodological challenges when monitoring the diet of pregnant women in a large cohort study; experiences from the Norwegian Mother and Child Cohort Study. Submitted.
Brantsæter AL, Haugen M, Alexander J, Meltzer HM. Validity of a new Food Frequency Questionnaire for pregnant women in the Norwegian Mother and Child Cohort Study (MoBa). Submitted.
Brantsæter AL, Haugen M, Rasmussen SE, Alexander J, Samuelsen SO and Meltzer HM. Urine flavonoids and plasma carotenoids in the validation of fruit, vegetable and tea intake during pregnancy in the Norwegian Mother and Child Cohort Study (MoBa). Public Health Nutrition, 2007 (in press).
Brantsæter AL, Haugen M, Julshamn K, Alexander J and Meltzer HM. Evaluation of urinary iodine excretion as a biomarker for intake of milk and dairy products in pregnant women in the Norwegian Mother and Child Cohort Study (MoBa).Submitted.
Brantsæter AL, Haugen M, Hagve TA, Aksnes L, Rasmussen SE, Julshamn K, Alexander J and Meltzer HM. Self-reported dietary supplement use is confirmed by biological markers the Norwegian Mother and Child Cohort Study (MoBa). Annals of Nutrition and Metabolism, 2007; 51 (in press).