British Journal of Nutrition

Dietary assessment and body composition

Validation of weighed records and other methods of dietary assessment using the 24 h urine nitrogen technique and other biological markers

S. A. Binghama1, A. Cassidya1, T. J. Colea2, A. Welcha1, S. A. Runswicka1, A. E. Blacka1, D. Thurnhama3, C. Batesa2, K. T. Khawa4, T. J. A. Keya5 and N. E. Daya6

a1 MRC Dunn Clinical Nutrition Centre, Hills Road, Cambridge CB2 2DH

a2 MRC Dunn Nutrition Unit, Downhams Lane, Milton Road, Cambridge CB4 1XJ

a3 Human Nutrition Group, Department of Biological and Biomedical Seiences, University of Ulster, Colerarine BT52 1SA

a4 Clinical Grantology Unit, F & G Block, Addenbrooke's Hospital, Cambridge CB2 2QQ

a5 Imperial Cancer Research Fund, Cancer Dpidemiology Unit, Gibson Building, The Radcliffe Infirmary, Oxford OX2 6HE

a6 Institute of Public Health, University Forvie Site, Robinson Way, Cambridge CB2 2SR


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 β-carotene and plasma vitamin C and β-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.

(Received April 15 1994)

(Revised July 15 1994)

(Accepted July 21 1994)