title: Urinary excretion of flavonoids reflects even small changes in the dietary intake of fruits and vegetables.
abstract: BACKGROUND
  Due to the random and systematic measurement errors associated with current dietary assessment instruments, there is a need to develop more objective methods of measuring the intake of foods of importance to human health.
  
  
  OBJECTIVE
  The purpose of this study was to test whether urinary excretion of flavonoids could be used to identify subjects who are meeting Norwegian recommendations for fruit and vegetable intake (5 servings per day) from individuals who are consuming the national average amount of fruits and vegetables (2 servings per day).
  
  
  METHODS
  Twenty-four-hour urine samples were collected in a strict crossover controlled feeding study. Forty healthy subjects (19-34 years) were included in the study. After a 1-week run-in period, one group was given a controlled diet that included 2 servings (300 g) of fruits and vegetables daily for 14 days, while the other group was given a diet containing 5 servings (750 g) per day. Following a 2-week washout and a 1 week run-in period, the regimens were switched between the groups.
  
  
  RESULTS
  An increased intake of mixed fruits and vegetables from 2 to 5 servings per day significantly enhanced urinary excretion of eriodictyol, naringenin, hesperetin, quercetin, kaempferol, isorhamnetin, and tamarixetin. The citrus flavonoids naringenin and hesperetin showed a steep dose-response relationship to dietary intake of fruits and vegetables, whereas the association to eriodictyol, quercetin, kaempferol, isorhamnetin, and tamarixetin was more moderate.
  
  
  CONCLUSIONS
  The present study indicates that urinary excretion of dietary flavonoids may be used to assess changes of mixed fruit and vegetable intake corresponding to an increase from the present national intake in Norway to the recommended amount of 5 servings of fruits and vegetables daily.
authors.affiliation: Institute for Nutrition Research, School of Medicine, University of Oslo, P. O. Box 1046, 0316 Oslo, Norway. asgeir.brevik@basalmed.uio.no
authors.forename: Asgeir
authors.initials: A
authors.lastname: Brevik
authors.forename: Salka Elbøl
authors.initials: SE
authors.lastname: Rasmussen
authors.forename: Christian A
authors.initials: CA
authors.lastname: Drevon
authors.forename: Lene Frost
authors.initials: LF
authors.lastname: Andersen
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D003718:Denmark; D004032:Diet; D005260:Female; D005419:Flavonoids / Q000378:metabolism / Q000652:urine*; D005638:Fruit / Q000378:metabolism*; D017408:Guidelines as Topic; D006801:Humans; D008297:Male; D009369:Neoplasms / Q000517:prevention & control; D009664:Norway; D018673:Nutrition Policy; D009751:Nutritional Requirements; D011336:Probability; D012016:Reference Values; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D014675:Vegetables / Q000378:metabolism*
chemical_list: D005419:Flavonoids