Targeted Urinary Profiling as a Biomarker of Dietary Flavonoid Intake from Fruits and Vegetables and its Relationship to the Timing of Dietary Assessment

Abstract

Background

Dietary intake of flavonoids, a class of plant (poly)phenols, is hypothesized to mediate a variety of beneficial health outcomes linked to fruits and vegetables (FV) intake. Absorbed flavonoids are metabolized and excreted in urine and may serve as biomarkers of FV intake and host metabolism, but defining the relationship of urinary biomarkers to the specific time of intake is unclear.

Objectives

To characterize a targeted panel of 6 urinary flavonoids and determine the relationship to estimated dietary flavonoid intake over time in adults.

Methods

Dietary flavonoid intake was estimated from both a 30-d food frequency questionnaire and 3-d diet records using the Phenol-Explorer database in 17 adults. Twenty-four-hour urine was collected, and a targeted panel of 6 urinary flavonoids (quercetin, phloretin, naringenin, hesperetin, kaempferol, and isorhamnetin) was quantified using high-pressure liquid chromatography-diode array detection (DAD).

Results

Compared to estimated intakes from a 1 d or 3 d diet record, total urinary flavonoids were most strongly associated with total FV (excluding potatoes) (r_s = 0.53, P = 0.028) and total FV flavonoid (r_s = 0.60, P = 0.011) intakes estimated by a 2 d diet record (including the day before and the day of the 24-h urine collection). There were no significant correlations between urinary concentrations of flavonoids and estimated FV intake using a 30-d food frequency questionnaire (r_s = 0.36, P = 0.16).

Conclusions

Targeted flavonoid concentrations in a 24-h urine collection may serve as a biomarker for estimating dietary exposures over 2 d prior to completion of the urine collection, but not more distant dietary exposures.

This trial was registered at clinicaltrials.gov as NCT03489213.