Strength of the relationships between three self-reported dietary intake instruments and serum carotenoids: the Observing Energy and Protein Nutrition (OPEN) Study

Objective: To assess the strength of the relationships between serum carotenoids and three self-reported dietary intake instruments often used to characterize carotenoid intake in studies of diet and disease. Design: Participants completed a Diet History Questionnaire (DHQ), two 24 h dietary recalls (24HR), a fruit and vegetable screener and a fasting blood draw. We derived dietary intake estimates of alpha-carotene, beta-carotene, cryptoxanthin, lutein, zeaxanthin and lycopene from each diet instrument and calculated sex-specific multivariate correlations between dietary intake estimates and their corresponding serum values. Setting: Montgomery County, Maryland, USA. Subjects: Four hundred and seventy women and men aged 40-69 years in the National Cancer Institute's Observing Protein and Energy Nutrition (OPEN) Study. Results: Serum carotenoids correlated more strongly with the DHQ (r = 0.34-0.54 for women; r = 0.38-0.56 for men) than with the average of two recalls (r = 0.26-0.47 for women; r = 0.26-0.40 for men) with the exception of zeaxanthin, for which the correlations using recalls were higher. With adjustment for within-person variation, correlations between serum carotenoids and recalls were greatly improved (r = 0.38-0.83 for women; r = 0.42-0.74 for men). In most cases, correlations between serum carotenoids and the fruit and vegetable screener resembled serum-DHQ correlations. Conclusions: Evidence from the study provides support for the use of the DHQ, fruit and vegetable screener and deattenuated recalls for estimating carotenoid status in studies without serum measures, and draws attention to the importance of adjusting for intra-individual variability when using recalls to estimate carotenoid values.