title: Comparing biological measurements of vitamin C, folate, alpha-tocopherol and carotene with 24-hour dietary recall information in nonhispanic blacks and whites.
abstract: OBJECTIVE
  To assess intake of several vitamins in preparation for a large cohort study investigating the effect of diet on risk of colon and prostate cancer.
  
  
  METHODS
  The dietary intake of several vitamins were assessed using eight different 24-hour recalls and a 200-item food frequency questionnaire (FFQ) from each subject. Participants also attended a clinic where blood was drawn and body composition, weight, height, and blood pressure were measured. A total of 97 black and 96 nonhispanic white subjects participated. The levels of alpha-tocopherol, carotene, folate, and vitamin C in the blood were correlated with the dietary intakes as measured by both 24-hour recalls and FFQ.
  
  
  RESULTS
  Correlations between blood levels and energy-adjusted dietary intake assessed by 24-hour recalls (with supplements) were as follows: carotene (adjusted for serum cholesterol): 0.47 and 0.55 in black and white subjects, respectively; alpha-tocopherol (adjusted for serum cholesterol): 0.61 (blacks) and 0.50 (whites); vitamin C: 0.22 (blacks) and 0.17 (whites); folate: 0.54 (blacks) and 0.55 (whites). Correlations between blood levels and FFQ indices were smaller in magnitude: 0.34 and 0.28 for carotene in black and white subjects, respectively, 0.37 and 0.56 for alpha-tocopherol (adjusted for serum cholesterol), 0.20 and 0.03 for vitamin C and 0.24 and 0.32 for folate.
  
  
  CONCLUSIONS
  The correlations observed were generally of modest to moderate size and were similar to or larger than those reported by others. This is despite variations in absorption, metabolism, and excretion of the vitamins and suggests that both the 24-hour recalls and the FFQ contain valid information.
authors.affiliation: Department of Epidemiology and Biostatistics, Loma Linda University, School of Public Health, Loma Linda, CA 92350, USA. sknutsen@sph.llu.edu
authors.forename: S F
authors.initials: SF
authors.lastname: Knutsen
authors.forename: G E
authors.initials: GE
authors.lastname: Fraser
authors.forename: K D
authors.initials: KD
authors.lastname: Linsted
authors.forename: W L
authors.initials: WL
authors.lastname: Beeson
authors.forename: D J
authors.initials: DJ
authors.lastname: Shavlik
mesh_terms: D001741:Black or African American / Q000706:statistics & numerical data*; D000886:Anthropometry; D001205:Ascorbic Acid / Q000097:blood; D002140:California; D002338:Carotenoids / Q000097:blood; D015331:Cohort Studies; D004034:Diet Surveys; D005492:Folic Acid / Q000097:blood; D011939:Mental Recall; D014810:Vitamin E / Q000097:blood; D014815:Vitamins / Q000097:blood*; D044465:White People / Q000706:statistics & numerical data*
chemical_list: D014815:Vitamins; D014810:Vitamin E; D002338:Carotenoids; D005492:Folic Acid; D001205:Ascorbic Acid