Validity and systematic error in measuring carotenoid consumption with dietary self-report instruments

Loki Natarajan, Shirley W. Flatt, Xiaoying Sun, Anthony C. Gamst, Jacqueline M. Major, Cheryl L. Rock, Wael Al-Delaimy, Cynthia A. Thomson, Vicky A. Newman, John P. Pierce

Research output: Contribution to journalArticlepeer-review

70 Scopus citations


Vegetables and fruits are rich in carotenoids, a group of compounds thought to protect against cancer. Studies of diet-disease associations need valid and reliable instruments for measuring dietary intake. The authors present a measurement error model to estimate the validity (defined as correlation between self-reported intake and "true" intake), systematic error, and reliability of two self-report dietary assessment methods. Carotenoid exposure is measured by repeated 24-hour recalls, a food frequency questionnaire (FFQ), and a plasma marker. The model is applied to 1,013 participants assigned between 1995 and 2000 to the nonintervention arm of the Women's Healthy Eating and Living Study, a randomized trial assessing the impact of a low-fat, high-vegetable/fruit/fiber diet on preventing new breast cancer events. Diagnostics including graphs are used to assess the goodness of fit. The validity of the instruments was 0.44 for the 24-hour recalls and 0.39 for the FFQ. Systematic error accounted for over 22% and 50% of measurement error variance for the 24-hour recalls and FFQ, respectively. The use of either self-report method alone in diet-disease studies could lead to substantial bias and error. Multiple methods of dietary assessment may provide more accurate estimates of true dietary intake.

Original languageEnglish (US)
Pages (from-to)770-778
Number of pages9
JournalAmerican journal of epidemiology
Issue number8
StatePublished - 2006


  • Bias (epidemiology)
  • Carotenoids
  • Diet
  • Models, statistical
  • Nutrition assessment
  • Reproducibility of results

ASJC Scopus subject areas

  • Epidemiology


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