Reliability and validity of self-report of vitamin and mineral supplement use in the vitamins and lifestyle study.
In the United States, dietary supplements contribute a large proportion of micronutrient intakes. Therefore, it is important to collect accurate information on supplement use for studies of micronutrients and disease risk. This report describes the test-retest reliability and validity of a detailed, self-administered mailed questionnaire on vitamin and mineral supplement use. Participants (n = 220) completed the questionnaire at baseline and 3 months later. During an in-person interview, participants provided spot urine and blood samples, and interviewers transcribed nutrient information from their supplement bottle labels. The questionnaire had very good test-retest reliability for mean supplement intake over the past 10 years, with intraclass correlations ranging from 0.69 for beta-carotene to 0.87 for vitamin E. Pearson's correlation coefficients comparing current supplemental intakes from the questionnaire and interviews/label transcriptions were high, ranging from 0.58 for beta-carotene to 0.82 for chromium; however, for some nutrients, median intakes from the questionnaire were slightly lower than from the interviews. Beta-carotene, vitamin C, and vitamin E (alpha-tocopherol) showed clear linear trends of increasing blood concentrations with higher self-reported supplemental intakes (Pearson's correlation coefficients adjusted for potential confounding factors and diet = 0.31, 0.29, and 0.69, respectively; all p < 0.0001). Creatinine-adjusted spot urinary calcium values were not associated with supplemental calcium intakes (Pearson's r = -0.07). This self-administered questionnaire demonstrated high reproducibility and validity for collecting detailed information on supplement use.
Department of Nutrition, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. jabouta@unc.edu
Jessie
J
Satia-Abouta
Ruth E
RE
Patterson
Irena B
IB
King
Kayla L
KL
Stratton
Ann L
AL
Shattuck
Alan R
AR
Kristal
John D
JD
Potter
Mark D
MD
Thornquist
Emily
E
White
D000368:Aged; D015415:Biomarkers / Q000097:blood; D004034:Diet Surveys; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D018977:Micronutrients; D008875:Middle Aged; D008903:Minerals / Q000008:administration & dosage*; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards; D014815:Vitamins / Q000008:administration & dosage*; D014861:Washington
D015415:Biomarkers; D018977:Micronutrients; D008903:Minerals; D014815:Vitamins