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-today 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.
|Journal||Journal of Nutrition|
|Publication status||Published - 2004|
- Single measurements