title: Objective assessment of dietary patterns by use of metabolic phenotyping: a randomised, controlled, crossover trial.
abstract: Accurate monitoring of changes in dietary patterns in response to food policy implementation is challenging. Metabolic profiling allows simultaneous measurement of hundreds of metabolites in urine, the concentrations of which can be affected by food intake. We hypothesised that metabolic profiles of urine samples developed under controlled feeding conditions reflect dietary intake and can be used to model and classify dietary patterns of free-living populations.
  
  
  
  In this randomised, controlled, crossover trial, we recruited healthy volunteers (aged 21-65 years, BMI 20-35 kg/m2) from a database of a clinical research unit in the UK. We developed four dietary interventions with a stepwise variance in concordance with the WHO healthy eating guidelines that aim to prevent non-communicable diseases (increase fruits, vegetables, whole grains, and dietary fibre; decrease fats, sugars, and salt). Participants attended four inpatient stays (72 h each, separated by at least 5 days), during which they were given one dietary intervention. The order of diets was randomly assigned across study visits. Randomisation was done by an independent investigator, with the use of opaque, sealed, sequentially numbered envelopes that each contained one of the four dietary interventions in a random order. Participants and investigators were not masked from the dietary intervention, but investigators analysing the data were masked from the randomisation order. During each inpatient period, urine was collected daily over three timed periods: morning (0900-1300 h), afternoon (1300-1800 h), and evening and overnight (1800-0900 h); 24 h urine samples were obtained by pooling these samples. Urine samples were assessed by proton nuclear magnetic resonance (1H-NMR) spectroscopy, and diet-discriminatory metabolites were identified. We developed urinary metabolite models for each diet and identified the associated metabolic profiles, and then validated the models using data and samples from the INTERMAP UK cohort (n=225) and a healthy-eating Danish cohort (n=66). This study is registered with ISRCTN, number ISRCTN43087333.
  
  
  
  Between Aug 13, 2013, and May 18, 2014, we contacted 300 people with a letter of invitation. 78 responded, of whom 26 were eligible and invited to attend a health screening. Of 20 eligible participants who were randomised, 19 completed all four 72 h study stays between Oct 2, 2013, and July 29, 2014, and consumed all the food provided. Analysis of1H-NMR spectroscopy data indicated that urinary metabolic profiles of the four diets were distinct. Significant stepwise differences in metabolite concentrations were seen between diets with the lowest and highest metabolic risks. Application of the derived metabolite models to the validation datasets confirmed the association between urinary metabolic and dietary profiles in the INTERMAP UK cohort (p<0·0001) and the Danish cohort (p<0·0001).
  
  
  
  Urinary metabolite models developed in a highly controlled environment can classify groups of free-living people into consumers of diets associated with lower or higher non-communicable disease risk on the basis of multivariate metabolite patterns. This approach enables objective monitoring of dietary patterns in population settings and enhances the validity of dietary reporting.
  
  
  
  UK National Institute for Health Research and UK Medical Research Council.
authors.affiliation: Nutrition and Dietetic Research Group, Division of Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK; Biomolecular Medicine, Division of Computational and Systems Medicine, Department of Surgery and Cancer, Imperial College London, London, UK.
authors.forename: Isabel
authors.initials: I
authors.lastname: Garcia-Perez
authors.affiliation: Biomolecular Medicine, Division of Computational and Systems Medicine, Department of Surgery and Cancer, Imperial College London, London, UK.
authors.forename: Joram M
authors.initials: JM
authors.lastname: Posma
authors.affiliation: Nutrition and Dietetic Research Group, Division of Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK.
authors.forename: Rachel
authors.initials: R
authors.lastname: Gibson
authors.affiliation: Nutrition and Dietetic Research Group, Division of Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK.
authors.forename: Edward S
authors.initials: ES
authors.lastname: Chambers
authors.affiliation: The Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Tue H
authors.initials: TH
authors.lastname: Hansen
authors.affiliation: The Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Vestergaard
authors.affiliation: The Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark.
authors.forename: Torben
authors.initials: T
authors.lastname: Hansen
authors.affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, UK.
authors.forename: Manfred
authors.initials: M
authors.lastname: Beckmann
authors.affiliation: The Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Oluf
authors.initials: O
authors.lastname: Pedersen
authors.affiliation: Department of Epidemiology and Biostatistics, Medical Research Council (MRC)-Public Health England Centre for Environment and Health, School of Public Health, Imperial College London, London, UK; MRC-National Institute for Health Research (NIHR) National Phenome Centre, Department of Surgery and Cancer, Imperial College London, London, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Elliott
authors.affiliation: Department of Preventive Medicine, Feinberg School of Medicine, Northwestern University, Chicago, USA.
authors.forename: Jeremiah
authors.initials: J
authors.lastname: Stamler
authors.affiliation: Biomolecular Medicine, Division of Computational and Systems Medicine, Department of Surgery and Cancer, Imperial College London, London, UK; MRC-National Institute for Health Research (NIHR) National Phenome Centre, Department of Surgery and Cancer, Imperial College London, London, UK.
authors.forename: Jeremy K
authors.initials: JK
authors.lastname: Nicholson
authors.affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, UK.
authors.forename: John
authors.initials: J
authors.lastname: Draper
authors.affiliation: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Newcastle, UK.
authors.forename: John C
authors.initials: JC
authors.lastname: Mathers
authors.affiliation: Biomolecular Medicine, Division of Computational and Systems Medicine, Department of Surgery and Cancer, Imperial College London, London, UK; MRC-National Institute for Health Research (NIHR) National Phenome Centre, Department of Surgery and Cancer, Imperial College London, London, UK. Electronic address: elaine.holmes@imperial.ac.uk.
authors.forename: Elaine
authors.initials: E
authors.lastname: Holmes
authors.affiliation: Nutrition and Dietetic Research Group, Division of Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, UK. Electronic address: g.frost@imperial.ac.uk.
authors.forename: Gary
authors.initials: G
authors.lastname: Frost
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000652:urine*; D018592:Cross-Over Studies; D004032:Diet; D005260:Female; D006801:Humans; D008297:Male; D055442:Metabolome; D055432:Metabolomics / Q000379:methods*; D008875:Middle Aged; D008954:Models, Biological; D010641:Phenotype; D055815:Young Adult
chemical_list: D015415:Biomarkers