Original Article
European Journal of Clinical Nutrition (2008) 62, 1131–1138; doi:10.1038/sj.ejcn.1602827; published online 30 May 2007
Development of a food frequency questionnaire for the assessment of quercetin and naringenin intake
Contributors: SR is principal investigator who coordinated and performed the study and drafted the manuscript, JMG is co-investigator who assisted in the formulation of the modified FFQ and helped in drafting the manuscript, LB developed software in Microsoft Access to extract and process information on nutrients and non-nutrients from the FFQ, GB is co-investigator who assisted the principal investigator in developing the method for quercetin and naringenin extraction, SS is co-investigator who assisted the principal investigator in developing the method for quercetin and naringenin extraction, PK is co-investigator who assisted the principal investigator in developing the method for quercetin and naringenin extraction and helped in drafting the manuscript, JS is statistician who helped in extracting the data from the FFQ and perform statistical analysis on the data in STATA 8.3 SE, ARH, is supervisor who planned the study and helped in drafting the manuscript, AC is supervisor who monitored the study and helped in drafting the manuscript, MR is supervisor who monitored the study and helped in drafting the manuscript, ITJ is chief investigator and supervisor who planned and monitored the study, and co-wrote the manuscript.
S Ranka1, J M Gee2, L Biro3, G Brett2, S Saha2, P Kroon2, J Skinner4, A R Hart5, A Cassidy4, M Rhodes1 and I T Johnson2
- 1Department of Surgery, Norfolk and Norwich University Hospital, Norwich, UK
- 2Institute of Food Research, Norfolk and Norwich University Hospital, Norwich, UK
- 3National Institute of Food Safety and Nutrition, Budapest, Hungary
- 4University of East Anglia, Norwich, UK
- 5Department of Gastroenterology, Norfolk and Norwich University Hospital, Norwich, UK
Correspondence: Professor IT Johnson, Gastrointestinal Biology & Health, Institute of Food Research, Colney Lane, Norwich, Norfolk, NR4 7UA, UK. E-mail: ian.johnson@bbsrc.ac.uk
Received 25 January 2007; Revised 27 March 2007; Accepted 30 April 2007; Published online 30 May 2007.
Abstract
Objectives:
To measure the relationship between quercetin and naringenin intakes as estimated by food frequency questionnaire (FFQ), and the urinary excretion of quercetin and naringenin aglycones after their enzymatic hydrolysis in human volunteers.
Subjects and methods:
Volunteers were recruited via the Human Nutrition Unit volunteer databank at the Institute of Food Research, Norwich. Sixty-three volunteers were recruited into the study, of which 14 were excluded and 49 completed the study. A modified FFQ was developed and used to estimate daily intake of quercetin and naringenin in 49 healthy volunteers who also provided five 24-h urine samples over a 2-week period. Urinary excretion of quercetin and naringenin metabolites was determined by solid-phase extraction and high-pressure liquid chromatography.
Results:
The estimated mean intakes of quercetin and naringenin were 29.4 mg (s.d. 15.0) and 58.1 mg (s.d. 62.7) per day, respectively. Mean urinary excretion of quercetin was 60.1 
g (s.d. 33.1) and that of naringenin was 0.56 mg (s.d. 0.4). The correlation between FFQ estimated intake of quercetin and naringenin and levels excreted in the urine were r=0.82 (P<0.0001) and r=0.25 (P=0.05), respectively.
Conclusions:
We observed a statistically significant correlation between the urinary excretion of quercetin and naringenin metabolites and their dietary intake as estimated by FFQ. Use of FFQs in epidemiological studies requiring an estimate of flavonoid intake seems justified.
Keywords:
cancer, flavonoids, quercetin, naringenin, portion size, FFQ
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