Calibration of citrus intake assessed by food frequency questionnaires using urinary proline betaine in an observational study setting

Yang Hu; Molin Wang; Walter C Willett; Meir Stampfer; Liming Liang; Frank B Hu; Eric Rimm; Lorraine Brennan; Qi Sun

doi:10.1016/j.ajcnut.2024.05.011

Calibration of citrus intake assessed by food frequency questionnaires using urinary proline betaine in an observational study setting

Am J Clin Nutr. 2024 May 16:S0002-9165(24)00474-X. doi: 10.1016/j.ajcnut.2024.05.011. Online ahead of print.

Authors

Yang Hu¹, Molin Wang², Walter C Willett³, Meir Stampfer³, Liming Liang², Frank B Hu³, Eric Rimm³, Lorraine Brennan⁴, Qi Sun⁵

Affiliations

¹ Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, United States.
² Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, United States; Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA, United States.
³ Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, United States; Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, United States; Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States.
⁴ Institute of Food and Health, School of Agriculture and Food Science, University College Dublin, Dublin, Ireland.
⁵ Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, United States; Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, United States; Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States. Electronic address: qisun@hsph.harvard.edu.

PMID: 38762186
DOI: 10.1016/j.ajcnut.2024.05.011

Abstract

Background: Whether observational study can be employed to establish calibration equations for self-reported dietary intake using food biomarkers is unknown.

Objectives: This study aims to demonstrate the feasibility of obtaining calibration equations based on food biomarkers and 7-d diet records (7DDRs) to correct measurement errors of food frequency questionnaires (FFQs) in an observational study setting.

Methods: The study population consisted of 669 males and 749 females from the Women's and Men's Lifestyle Validation Studies. In the training set, the biomarker-predicted intake derived by regressing 7DDR-assessed intake on urinary proline betaine concentration was regressed on the FFQ-assessed intake to obtain the calibration equations. The regression coefficients were applied to the test set to calculate the calibrated FFQ intake. We examined total citrus as well as individual citrus fruits/beverages.

Results: Urinary proline betaine was moderately correlated with orange juice intake (Pearson correlation [r] = 0.53 for 7DDR and 0.48 for FFQ) but only weakly correlated with intakes of orange (r = 0.12 for 7DDR and 0.15 for FFQ) and grapefruit (r = 0.14 for 7DDR and 0.09 for FFQ). The FFQ-assessed citrus intake was systematically higher than the 7DDR-assessed intake, and after calibrations, the mean calibrated FFQ measurements were almost identical to 7DDR assessments. In the test set, the mean intake levels from 7DDRs, FFQs, and calibrated FFQs were 62.5, 75.3, and 63.2 g/d for total citrus; 41.6, 42.5, and 41.9 g/d for orange juice; 11.8, 24.3, and 12.3 g/d for oranges; and 8.3, 9.3, and 8.6 g/d for grapefruit, respectively. We observed larger differences between calibrated FFQ and 7DDR assessments at the extreme ends of intake, although, on average, good agreements were observed for all citrus except grapefruit.

Conclusions: Our 2-step calibration approach has the potential to be adapted to correct systematic measurement error for other foods/nutrients with established food biomarkers in a cost effective way.

Keywords: NMR-spectroscopy; calibration analysis; diet records; measurement error; urinary food biomarker.