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Nutritional Epidemiology

Reproducibility of Plasma Alkylresorcinols during a 6-Week Rye Intervention Study in Men with Prostate Cancer^1,2

³ Department of Food Science, Swedish University of Agriculture Science, SE-75007 Uppsala, Sweden; ⁴ Clinic of Urology, Örebro University Hospital, SE-701 85 Örebro, Sweden; and ⁵ Nutrition Research, Department of Public Health and Clinical Medicine, University of Umeå, SE-90187 Umeå, Sweden

Alkylresorcinols (AR), phenolic lipids exclusively present in the outer parts of wheat and rye grains, have been proposed as concentration biomarkers of whole-grain wheat and rye intake. A key feature of a good biomarker is high reproducibility, which indicates how accurately a single sample reflects the true mean biomarker concentration caused by a certain intake. In this study, the short- to medium-term reproducibility of plasma AR was determined using samples from a crossover intervention study, where men with prostate cancer (n = 17) were fed rye whole-grain/bran or refined wheat products for 6-wk periods. AR homologs C17:0 and C21:0 differed between the treatments (P < 0.001). The reproducibility determined by the intraclass correlation coefficient (ICC) was high (intervention period 1: ICC = 0.90 [95% CI = 0.82–0.98], intervention period 2: ICC = 0.88 [95% CI = 0.78–0.98]). The results show that a single fasting plasma sample could be used to estimate the mean plasma AR concentration during a 6-wk intervention period with constant intake at a precision of ± 20% (80% CI). This suggests that the plasma AR concentration can be used as a reliable short- to medium-term biomarker for whole-grain wheat and rye under intervention conditions where intake is kept constant.

^* To whom correspondence should be addressed. E-mail: rikard.landberg{at}lmv.slu.se.

Manuscript received 22 September 2008. Initial review completed 17 October 2008. Revision accepted 2 February 2009.

Published online 25 March 2009.