title: Metabolic profiling strategy for discovery of nutritional biomarkers: proline betaine as a marker of citrus consumption.
abstract: BACKGROUND
  New food biomarkers are needed to objectively evaluate the effect of diet on health and to check adherence to dietary recommendations and healthy eating patterns.
  
  
  OBJECTIVE
  We developed a strategy for food biomarker discovery, which combined nutritional intervention with metabolic phenotyping and biomarker validation in a large-scale epidemiologic study.
  
  
  METHODS
  We administered a standardized diet to 8 individuals and established a putative urinary biomarker of fruit consumption by using (1)H nuclear magnetic resonance (NMR) spectroscopic profiling. The origin of the biomarker was confirmed by using targeted NMR spectroscopy of various fruit. Excretion kinetics of the biomarker were measured. The biomarker was validated by using urinary NMR spectra from UK participants of the INTERMAP (International Collaborative Study of Macronutrients, Micronutrients, and Blood Pressure) (n = 499) in which citrus consumption was ascertained from four 24-h dietary recalls per person. Finally, dietary patterns of citrus consumers (n = 787) and nonconsumers (n = 1211) were compared.
  
  
  RESULTS
  We identified proline betaine as a putative biomarker of citrus consumption. High concentrations were observed only in citrus fruit. Most proline betaine was excreted < or =14 h after a first-order excretion profile. Biomarker validation in the epidemiologic data showed a sensitivity of 86.3% for elevated proline betaine excretion in participants who reported citrus consumption and a specificity of 90.6% (P < 0.0001). In comparison with noncitrus consumers, citrus consumers had lower intakes of fats, lower urinary sodium-potassium ratios, and higher intakes of vegetable protein, fiber, and most micronutrients.
  
  
  CONCLUSIONS
  The biomarker identification and validation strategy has the potential to identify biomarkers for healthier eating patterns associated with a reduced risk of major chronic diseases. The trials were registered at clinicaltrials.gov as NCT01102049 and NCT01102062.
authors.affiliation: Biomolecular Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom.
authors.forename: Silke S
authors.initials: SS
authors.lastname: Heinzmann
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Brown
authors.forename: Queenie
authors.initials: Q
authors.lastname: Chan
authors.forename: Magda
authors.initials: M
authors.lastname: Bictash
authors.forename: Marc-Emmanuel
authors.initials: ME
authors.lastname: Dumas
authors.forename: Sunil
authors.initials: S
authors.lastname: Kochhar
authors.forename: Jeremiah
authors.initials: J
authors.lastname: Stamler
authors.forename: Elaine
authors.initials: E
authors.lastname: Holmes
authors.forename: Paul
authors.initials: P
authors.lastname: Elliott
authors.forename: Jeremy K
authors.initials: JK
authors.lastname: Nicholson
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000652:urine*; D002957:Citrus; D004032:Diet; D005260:Female; D005638:Fruit; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009752:Nutritional Status; D028321:Plant Preparations / Q000493:pharmacokinetics*; D011392:Proline / Q000031:analogs & derivatives* / Q000652:urine
chemical_list: D015415:Biomarkers; D028321:Plant Preparations; D011392:Proline; C003342:stachydrine