Alkylresorcinols as biomarkers of whole-grain intake

Background: In order to attenuate the measurement error inherent in dietary recall methods, alkylresorcinols (ARs) have been proposed as a biomarker of whole-grain (WG) intake. Although ARs have shown promise in experimental and observational studies, most of this research has been conducted in Nordic populations that consume relatively high amounts of WG. Objectives: The objectives of this study were to assess the utility of plasma AR concentration as a WG intake biomarker and identify the primary dietary and non-dietary determinants of plasma AR concentration in a population that consumes relatively few WG. Methods: This ancillary study used data from first-year college students (n=122) who completed three interviewer-administered 24-hour recalls and had two fasting venous blood draws performed on non-consecutive days. Dietary data was compiled using the Nutrition Data System for Research. Blood lipids and glucose were determined via enzymatic assay and plasma AR concentrations were determined by gas chromatography-mass spectrometry. Correlation coefficients were calculated between plasma AR concentrations and dietary intake variables and cardiometabolic risk factors. One-way ANOVA and Tukey’s post-hoc test were used to assess group differences across plasma AR quartiles. Determinants of plasma AR concentration were assessed using multiple regression models. Statistical analyses were performed using R version 3.2.3. Results: Plasma AR concentration was significantly positively correlated with WG intake (rs = 0.24, p \u3c0.01). The correlation was stronger in males (n=36, rs = 0.33, p \u3c 0.05) than females (n=86, rs = 0.18, p = 0.08). One-way ANOVA across plasma AR quartiles was significant for fiber intake [F(3,118) = 8.58, p \u3c 0.001] and Tukey’s HSD test showed that the mean daily fiber intake for the highest AR quartile was significantly greater than for the lowest (M = 20.2 ± 1.9 g, 14.7 ± 1.4 g respectively). The only cardiometabolic risk factor that was significantly associated with plasma AR concentration was triglycerides (rs = 0.27, p \u3c 0.01). Multiple regression models including log-transformed dietary variables showed that WG bread was the only significant food-item predictor of plasma AR concentration (β = 0.54, p \u3c 0.01). Conclusions: Although plasma AR concentration was significantly associated with WG and fiber intake, triglycerides were the primary determinant and the relationships were not strong enough to produce accurate WG intake prediction models. More research is needed on the use of AR as a quantitative biomarker in low WG-consuming populations