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.
Satia-Abouta
Jessie
J
Department of Nutrition, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. jabouta@unc.edu
Patterson
Ruth E
RE
King
Irena B
IB
Stratton
Kayla L
KL
Shattuck
Ann L
AL
Kristal
Alan R
AR
Potter
John D
JD
Thornquist
Mark D
MD
White
Emily
E
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