title: Absorption estimates improve the validity of the relationship between dietary and serum lycopene.
abstract: OBJECTIVE
  Studies show low correlations between dietary intake and serum concentrations of lycopene, which make it difficult to assess the effectiveness of dietary interventions with this phytonutrient. We hypothesized that 1) combining food-frequency questionnaires (FFQs) and 3-d diet records (3D-DRs) by the triads method would improve the validity of this relation and 2) correcting dietary information for differences in lycopene absorption from food matrices would further improve validity.
  
  
  METHODS
  We measured dietary intakes of lycopene from 49 adults by 3D-DR and FFQ. Serum lycopene was measured by high-performance liquid chromatography with diode array detection. Cholesterol and triacylglycerol concentrations were measured spectrophotometrically. Lycopene-containing foods were given absorption factors based on literature and laboratory values. Associations between dietary and serum lycopene were modeled using multiple regression. The triads method was used for validation of relations among FFQ, 3D-DR, and serum lycopene.
  
  
  RESULTS
  Raw data showed low correlations between dietary and serum lycopene (r=+0.15 for 3D-DR, +0.35 for FFQ). Mathematical modeling showed that the 3D-DR and FFQ methods must be used to collect accurate dietary information for lycopene. Validity coefficients calculated by the triads method were +0.34 for 3D-DR and +0.78 for FFQ. Correcting for absorption increased the validity coefficient to +0.72 for 3D-DR and from +0.45 to +0.66 for serum lycopene.
  
  
  CONCLUSIONS
  The relation between dietary intake and serum concentrations of lycopene and other carotenoids can be improved by collecting 3D-DR and FFQ data and by adjusting dietary information for nutrient absorption.
authors.affiliation: Western Human Nutrition Research Center, United States Department of Agriculture, Davis, California, USA. betty.burri@ars.usda.gov
authors.forename: Betty Jane
authors.initials: BJ
authors.lastname: Burri
authors.forename: Thuan
authors.initials: T
authors.lastname: Nguyen
authors.forename: Terry R
authors.initials: TR
authors.lastname: Neidlinger
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D002338:Carotenoids / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid; D004032:Diet; D015930:Diet Records; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D000077276:Lycopene; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D011795:Surveys and Questionnaires
chemical_list: D000975:Antioxidants; D002338:Carotenoids; D000077276:Lycopene