New alkylresorcinol metabolites in spot urine as biomarkers of whole grain wheat and rye intake in a Swedish middle-aged population

Background/objectives: Studies on the health effects of whole grains typically use self-reported intakes which are prone to large measurement errors. Dietary biomarkers that can provide an objective measure of intake are needed. New alkylresorcinol (AR) metabolites (3,5-dihydroxycinnamic acid (DHCA), 2-(3,5-dihydroxybenzamido)acetic acid (DHBA-glycine) and 5-(3,5-dihydroxyphenyl) pentanoic acid (DHPPTA)) in 24 h urine samples have been suggested as biomarkers for whole grain (WG) wheat and rye intake but remain to be evaluated in spot urine samples. Subjects/methods: The reproducibility of the new AR metabolites (DHCA, DHBA-glycine and DHPPTA) was investigated in 4 repeated samples over a period of 2 wk in spot urine from 40 Swedish men and women enroled in the SCAPIS-study, after adjustment of creatinine. Metabolite concentrations were correlated with total whole grain intake estimated during the same period. Results: The medium-term reproducibility determined for DHCA, DHPPTA and DHBA-glycine varied from moderate to excellent (intra-class correlation coefficient = 0.35–0.67). Moreover, DHCA and DHBA-glycine were independently associated with self-reported total WG intake (β = 0.18, P = 0.08 and β = 0.18, P = 0.02, respectively) and all metabolites except for DHPPA were higher among women. Conclusions: This study supports the idea of using AR metabolites in one or several spot urine samples as biomarkers of whole grain intake. These findings need to be confirmed in different populations