Reliability and Validity of Self-Report of Vitamin and Mineral Supplement Use in the Vitamins and Lifestyle Study

• Published in: American journal of epidemiology Vol. 157; no. 10; pp. 944 - 954
• Main Authors: Satia-Abouta, Jessie, Patterson, Ruth E., King, Irena B., Stratton, Kayla L., Shattuck, Ann L., Kristal, Alan R., Potter, John D., Thornquist, Mark D., White, Emily
• Format: Journal Article
• Language: English
• Published: Cary, NC Oxford University Press 15.05.2003; Oxford Publishing Limited (England)
• Subjects: Abbreviation: VITAL; Aged; Biological and medical sciences; Biomarkers - blood; Diet Surveys; dietary supplements; Female; Human physiology applied to population studies and life conditions. Human ecophysiology; Humans; Life Style; Male; Medical sciences; Micronutrients; Middle Aged; Minerals - administration & dosage; Nutritional survey. Food supply and nutritional requirement; questionnaires; reliability; Reproducibility of Results; Surveys and Questionnaires - standards; validity; vitamins; Vitamins - administration & dosage; Vitamins and Lifestyle; Washington; Washington; Human; Questionnaire; Nutrition survey; Vitamin; Minerals; Test reliability; questionnaires; reproducibility of results; Validity; vitamins; Reproducibility; dietary supplements; Reliability; Food supplement
• ISSN: 0002-9262; 1476-6256; 0002-9262
• DOI: 10.1093/aje/kwg039

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.