Alkylresorcinol metabolites in urine correlate with the intake of whole grains and cereal fibre in free-living Swedish adults.
ABSTRACT Alkylresorcinols (AR) have been established as short/medium-term biomarkers for whole grain (WG) wheat and rye intake; and AR metabolites, 3,5-dihydroxybenzoic acid and 3-(3,5-dihydroxyphenyl)-propanoic acid, have been suggested as complementary biomarkers to AR. The present study examined the medium-term reproducibility and relative validity of urinary AR metabolites as biomarkers for WG and cereal fibre intake. A total of sixty-six free-living Swedes completed 3 d weighed food records and provided single 24 h urine collections and morning urine spot samples on two occasions, 2-3 months apart. The medium-term reproducibility of urinary AR metabolites was moderate when assessed in 24 h collections and lower in creatinine (CR)-adjusted morning urine. Mean AR metabolite 24 h excretions correlated well with total WG (rs 0·31-0·52, P < 0·05) and cereal fibre (rs 0·46-0·58, P < 0·001) intake on both occasions. As expected, correlations with WG (rs 0·28-0·38, P < 0·05) and cereal fibre (rs 0·35-0·42, P < 0·01) were weaker for mean CR-adjusted AR metabolite concentrations in spot samples of morning urine, although the adjusted concentrations correlated well with 24 h urinary excretion (rs 0·69-0·73, P < 0·001). Adjustment for intra-individual variations substantially improved the correlations between intake and excretion. These findings suggest that urinary AR metabolites can successfully reflect the medium-term intake of WG and cereal fibre when adjusted for intra-individual variation in this population, where rye was the major contributor to high WG intake. The performance of urinary AR metabolites as medium-term biomarkers appears to be comparable to that of fasting plasma AR concentration in this population.
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ABSTRACT: When measuring biomarkers in urine, volume (and time) or concentration of creatinine are both accepted methods of standardization for diuresis. Both types of standardization contribute uncertainty to the final result. The aim of the present paper was to compare the uncertainty introduced when using the two types of standardization on 24 h samples from healthy individuals. Estimates of uncertainties were based on results from the literature supplemented with data from our own studies. Only the difference in uncertainty related to the two standardization methods was evaluated. It was found that the uncertainty associated with creatinine standardization (19-35%) was higher than the uncertainty related to volume standardization (up to 10%, when not correcting for deviations from 24 h) for 24 h urine samples. However, volume standardization introduced an average bias of 4% due to missed volumes in population studies. When studying a single 24 h sample from one individual, there was a 15-20% risk that the sample was incomplete. In this case a bias of approximately 25% was introduced when using volume standardization, whereas the uncertainty related to creatinine standardization was independent of the completeness of the sample. The uncertainty of creatinine standardization is increased when studying single voids rather than 24 h urine samples. This is partially counteracted by the increased statistical power due to the increased number of samples for each individual. Furthermore, there is a considerable increase in convenience for the participants, when collecting small volumes rather than complete 24 h samples.Annals of Occupational Hygiene 04/2004; 48(2):171-9. · 2.16 Impact Factor
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ABSTRACT: Estimation of dietary intake of polyphenols is difficult, due to limited availability of food composition data and bias inherent to dietary assessment methods. The aim of the present study was to evaluate whether we could detect polyphenols and their metabolites in a spot urine sample in a free-living human population and whether it was related to those observed in 24-h urine samples, for potential use as a biomarkers of polyphenol intake. Four 24-h urine samples and two spot urine samples were collected from 154 participants of the SU.VI.MAX cohort (a randomized primary-prevention trial evaluating the effect of daily antioxidant supplementation on chronic diseases) in two separate studies over, respectively, a 7- and 2-day periods. Thirteen polyphenols and metabolites (chlorogenic acid (CGA), caffeic acid (CA), m-coumaric acid (mCOU), gallic acid (GA), 4-O-methylgallic acid (MeGA), quercetin (Q), isorhamnetin (MeQ), kaempferol (K), hesperetin (HESP), naringenin (NAR), phloretin (PHLOR), enterolactone (ENL) and enterodiol (END) were measured using HPLC-ESI-MS-MS. Correlations between the urinary excretion levels were observed. The most significant were explained by metabolic filiations (CGA/CA, CA/mCOU, GA/MeGA, Q/MeQ, NAR/PHLOR, ENL/END) or co-occurrence in a same food source (NAR/HESP). Concentrations in spot samples correlated with those in 24-h urine sample (P<0.02, except for CA and for MeQ). Intra-individual variations were smaller than inter-individual variations for all polyphenols (P<0.01) except for MeGA and for PHLOR. These results show that these polyphenols and metabolites are useful biomarkers for polyphenol intake.European Journal of Clinical Nutrition 04/2008; 62(4):519-25. · 2.76 Impact Factor
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ABSTRACT: Alkylresorcinols (ARs), phenolic lipids exclusively present in the outer parts of wheat and rye grains, have been proposed as specific dietary biomarkers of whole-grain wheat and rye intake. The objective was to validate plasma ARs as a biomarker of whole-grain wheat and rye intakes by studying the correlation between their plasma concentration and intake calculated from food records. In a randomized crossover study, 22 women and 8 men were given a defined amount of either whole-grain or refined-cereal-grain products to be included in their habitual diets for two 6-wk periods. Blood samples were collected and food intakes were recorded before and after each intervention period. Plasma AR concentrations were significantly higher after the whole-grain diet period than after the refined-grain period (P < 0.0001) and were well correlated with average daily AR intake estimated by self-reported weighed food records (Spearman's r = 0.58, P < 0.001). Plasma AR concentrations are correlated with intake assessed by food records, which suggests that ARs are selective nutritional biomarkers for the intake of whole-grain wheat and rye.American Journal of Clinical Nutrition 04/2008; 87(4):832-8. · 6.50 Impact Factor