title: A single measurement is inadequate to estimate enterolactone levels in danish postmenopausal women due to large intraindividual variation.
abstract: Single measurements of enterolactone (ENL) used in epidemiologic studies are influenced by intraindividual variation. The objective of this controlled study was to investigate short-term intraindividual variations in serum and urine ENL. Based on these variations, the number of samples required to describe the basal ENL level was estimated. Healthy Danish postmenopausal women (n = 6) aged 54-67 y completed 3 study periods of 24 h within 2 mo. Blood samples were collected at 0, 4, 6, 8, 12, and 24 h and 24-h urine samples were collected. A low-lignan, standardized diet of 3 meals was served. ENL was measured by time-resolved fluoroimmunoassay. Intraindividual and interindividual variations were estimated using a mixed model with repeated measurements. Significant and systematic intraindividual within-day variations (CV) of 31% were observed in serum. Intraindividual day-to-day variations were 56% and overall intraindividual variation of samples collected at random times and on different days was estimated to be 64%. Describing this overall variation required 7 blood samples when estimated with a precision of 50% and 95% confidence. Day-to-day variations in 24-h urine samples were 49%. Large within-day and day-to-day variations suggest that a single measurement of ENL is inadequate to estimate the basal ENL level.
authors.affiliation: The Department of Human Nutrition, Centre for Advanced Food Studies, The Royal Veterinary and Agricultural University, Frederiksberg, Denmark. hlh@kvl.dk
authors.forename: Helene
authors.initials: H
authors.lastname: Hausner
authors.forename: Nina F
authors.initials: NF
authors.lastname: Johnsen
authors.forename: Jesper
authors.initials: J
authors.lastname: Hallund
authors.forename: Inge
authors.initials: I
authors.lastname: Tetens
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000097:blood* / Q000652:urine*; D000368:Aged; D002940:Circadian Rhythm; D003718:Denmark; D005260:Female; D015200:Fluoroimmunoassay; D006801:Humans; D017705:Lignans / Q000097:blood* / Q000652:urine*; D008875:Middle Aged; D008954:Models, Biological; D017698:Postmenopause / Q000097:blood* / Q000652:urine*; D011897:Random Allocation
chemical_list: D017705:Lignans; D015107:4-Butyrolactone; C029497:2,3-bis(3'-hydroxybenzyl)butyrolactone