Free fruit at workplace intervention increases total fruit intake: a validation study using 24 h dietary recall and urinary flavonoid excretion

Eur J Clin Nutr. 2010 Oct;64(10):1222-8. doi: 10.1038/ejcn.2010.130. Epub 2010 Aug 4.


Background/objectives: To validate 24 h dietary recall of fruit intake by measuring the total 24 h excretion of 10 different flavonoids in 24 h urine during an intervention with free fruit at workplaces.

Subjects/methods: Employees at workplaces offering a free-fruit program, consisting of daily free and easy access to fresh fruit, and controls employees at workplaces with no free-fruit program were enrolled in this validation study (n=103). Dietary intake was assessed by using a 24 h dietary recall questionnaire at baseline and approximately 5 months later. Ten flavonoids, quercetin, isorhamnetin, tamarixetin, kaempferol, hesperetin, naringenin, eriodictyol, daidzein, genistein, and phloretin, were measured using HPLC-electrospray ionization-MS.

Results: The 24 h urinary excretion of total flavonoids and the estimated intake of fruits were significantly correlated (r (s)=0.31, P<0.01). The dietary intake of citrus fruits and citrus juices was significantly correlated with total excretion of citrus specific flavonoids (r (s)=0.28, P<0.01), and orange was positively correlated with naringenin (r (s)=0.24, P<0.01) and hesperetin (r (s)=0.24, P<0.01). Phloretin in urine was correlated with apple intake (r (s)=0.22, P<0.01) and also with overall estimated intake of fruit (r (s)=0.22, P<0.01).

Conclusions: This study shows that a 24 h dietary recall can be used as a valid estimate of the intake of fruits in agreement with an objective biomarker of fruit intake in free fruit at workplace interventions.

Publication types

  • Controlled Clinical Trial
  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Biomarkers / chemistry
  • Biomarkers / urine
  • Diet*
  • Flavonoids / chemistry
  • Flavonoids / urine*
  • Fruit / economics*
  • Health Promotion / methods*
  • Humans
  • Placebo Effect
  • Reproducibility of Results
  • Surveys and Questionnaires
  • Workplace*


  • Biomarkers
  • Flavonoids