title: Validation of weighed records and other methods of dietary assessment using the 24 h urine nitrogen technique and other biological markers.
abstract: Results from analysis of 24 h urine collections, verified for completeness with para-amino benzoic acid, and blood samples collected over 1 year were compared with 16 d weighed records of all food consumed collected over the year, and with results from 24 h recalls, food-frequency questionnaires and estimated food records in 160 women. Using the weighed records, individuals were sorted into quintiles of the distribution of the urine N excretion:dietary N intake ratio (UN:DN). UN exceeded DN in the top quintile of this ratio; mean ratio UN:DN = 1.13. Individuals in this top quintile were heavier, had significantly greater body mass indices, were reportedly more restrained eaters, had significantly lower energy intake:basal metabolic rate ratios (EI:BMR), and had correlated ratios of UN:DN and EI:BMR (r -0.62). Those in the top quintile reported lower intakes of energy and energy-yielding nutrients, Ca, fats, cakes, breakfast cereals, milk and sugars than individuals in the other quintiles but not lower intakes of non-starch polysaccharides, vitamin C, vegetables, potatoes or meat. Correlations between dietary intake from weighed records and 24 h urine K were 0.74 and 0.82, and between dietary vitamin C and beta-carotene and plasma vitamin C and beta-carotene 0.86 and 0.48. Correlations between dietary N intake from weighed records and 24 h urine excretion were high (0.78-0.87). Those between N from estimated food records and urine N were r 0.60-0.70. Correlations between urine N and 24 h recalls and food-frequency questionnaires were in the order of 0.01 to 0.5. Despite problems of underreporting in overweight individuals in 20% of this sample, weighed records remained the most accurate method of dietary assessment, and only an estimated 7 d diary was able to approach this accuracy.
authors.affiliation: MRC Dunn Clinical Nutrition Centre, Cambridge.
authors.forename: S A
authors.initials: SA
authors.lastname: Bingham
authors.forename: A
authors.initials: A
authors.lastname: Cassidy
authors.forename: T J
authors.initials: TJ
authors.lastname: Cole
authors.forename: A
authors.initials: A
authors.lastname: Welch
authors.forename: S A
authors.initials: SA
authors.lastname: Runswick
authors.forename: A E
authors.initials: AE
authors.lastname: Black
authors.forename: D
authors.initials: D
authors.lastname: Thurnham
authors.forename: C
authors.initials: C
authors.lastname: Bates
authors.forename: K T
authors.initials: KT
authors.lastname: Khaw
authors.forename: T J
authors.initials: TJ
authors.lastname: Key
mesh_terms: D001481:Basal Metabolism; D015415:Biomarkers / Q000652:urine; D015992:Body Mass Index; D001835:Body Weight; D004032:Diet; D015930:Diet Records; D002149:Energy Intake; D005260:Female; D006801:Humans; D008875:Middle Aged; D009584:Nitrogen / Q000008:administration & dosage / Q000652:urine*; D015203:Reproducibility of Results
chemical_list: D015415:Biomarkers; D009584:Nitrogen