Validation of Reported Whole-Grain Intake from a Web-Based Dietary Record against Plasma Alkylresorcinol Concentrations in 8-to 11-Year-Olds Participating in a Randomized Controlled Trial

Background: Whole-grain (WG) intake is important for human health, but accurate intake estimation is challenging. Use of a biomarker for WG intake provides a possible way to validate dietary assessment methods. Objective: Our aim was to validate WG intake from 2 diets reported by children, using plasma alkylresorcinol (AR) concentrations, and to investigate the 3-mo reproducibility of AR concentrations and reported WG intake. Methods: AR concentrations were analyzed in fasting blood plasma samples, and WG intake was estimated in a 7-d web based diary by 750 participants aged 8-11 y in a 2 school meal x 3 mo crossover trial. Reported WG intake and plasma AR concentrations were compared when children ate their usual bread-based lunch (UBL) and when served a hot lunch meal (HLM). Correlations and cross-classification were used to rank subjects according to intake. The intraclass correlation coefficients (ICCs) between subjects' measurements-at baseline and after the UBL were used to assess reproducibility. Results: Correlations between reported WG wheat + rye intake and plasma AR were 0.40 and 0.37 (P< 0.001) for the UBL and the HLM diets, and 78% and 77% were classified in the same or adjacent quartiles for the UBL and HLM diets, respectively. The ICC over 3 mo was 0.47 (95% CI: 0,38, 0.55) for plasma total ARs and 0.64 (95% CI: 0.58 , 0.70) for reported WG intake. Correlations were higher when using the AR C17:0 homolog as a biomarker, reflecting rye intake instead of plasma total ARs [UBL: r= 0.47; HLM: r= 0.43, P< 0.001; ICC = 0.51 (95% CI: 0.43, 0.59)]. Conclusions: Self-reported WG wheat + rye intake among children showed moderate correlations with plasma AR concentrations. Substantial intraindividual variation was found in WG intake and plasma AR concentrations. The AR homolog C17:0 may be used as a biomarker for WG intake when the WG intake primarily comes from rye as in the present study. This trial was registered at clinicaltrials.gov as NCT01457794.