title: Calibration of a semi-quantitative food frequency questionnaire in early pregnancy.
abstract: OBJECTIVE
  We assessed the validity of a semi-quantitative food frequency questionnaire (FFQ) among pregnant women.
  
  
  METHODS
  We enrolled 72 African American and 132 Caucasian pregnant women in a calibration study of an existing FFQ. For eight categories of intake of fatty acids, carotenoids, and gamma- tocopherol estimated by the FFQ (energy-adjusted deciles 1, 2, 3, 4+5, 6+7, 8, 9, 10) we compared measurements of the corresponding nutrient level measured in pooled blood specimens from all participants in each category.
  
  
  RESULTS
  For alpha-carotene, plasma levels were 1.9 (p=0.10) and 2.9 (p=0.0007) microg/L higher for every 100 microg increase in dietary intake among African American and Caucasian women, respectively. A high percent increase in plasma levels was apparent between extreme dietary deciles of alpha-carotene (275% for African American and 152% for Caucasian women). Increases across deciles were evident for lycopene, lutein, and gamma-tocopherol, ranging from 12% to 64%. We also observed relationships between dietary intake and their erythrocyte concentrations of long-chain n-3 fatty acids and trans-fatty acids, but not alpha-linolenic acid.
  
  
  CONCLUSIONS
  The observed differences in biomarkers across varying levels of dietary intake suggest that this FFQ is an appropriate epidemiologic tool for assessing intake of at least several important nutrients during early pregnancy in both African American and Caucasian women.
authors.affiliation: Department of Nutrition, Harvard School of Public Health and Harvard Pilgrim Health Care, Boston, MA. mina@hsph.harverd.edu
authors.forename: Wafaie W
authors.initials: WW
authors.lastname: Fawzi
authors.forename: Sheryl L
authors.initials: SL
authors.lastname: Rifas-Shiman
authors.forename: Janet W
authors.initials: JW
authors.lastname: Rich-Edwards
authors.forename: Walter C
authors.initials: WC
authors.lastname: Willett
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Gillman
mesh_terms: D000328:Adult; D001741:Black or African American; D000975:Antioxidants / Q000378:metabolism*; D015415:Biomarkers / Q000097:blood; D002338:Carotenoids / Q000097:blood*; D004032:Diet; D005227:Fatty Acids / Q000097:blood; D005260:Female; D006801:Humans; D014975:Lutein / Q000097:blood; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood*; D011795:Surveys and Questionnaires; D044465:White People; D024504:gamma-Tocopherol / Q000097:blood
chemical_list: D000975:Antioxidants; D015415:Biomarkers; D005227:Fatty Acids; D002338:Carotenoids; D024504:gamma-Tocopherol; D014975:Lutein