Plasma alkylresorcinol concentrations correlate with whole grain wheat and rye intake and show moderate reproducibility over a 2- to 3-month period in free-living Swedish adults.

Plasma alkylresorcinols (AR) are useful as dietary biomarkers of wheat and rye whole grain (WG) during interventions but need to be validated in free-living populations. This study estimated the medium-term reproducibility and relative validity of plasma AR as biomarkers of WG and cereal fiber intake. Seventy-two Swedish adults kept 3-d weighed food records on 2 occasions 2-3 mo apart. Of these men and women, 51 provided a fasting blood sample at the end of each occasion. In addition, 18 participants provided 3 fasting and 3 nonfasting samples for 3 consecutive days on the first and second occasions, respectively. Dietary and blood variables did not differ between the 2 occasions. Nonfasting plasma total AR concentration [210 nmol/L (95% CI: 140, 314)] was higher than fasting [99 nmol/L (95% CI: 72, 137)] (P < 0.0001). Mean WG intake was 70 ± 61 g/d (41% from rye) and the intra-class correlation coefficient was 0.44 (95% CI: 0.26, 0.63) for total WG intake and 0.47 (95% CI: 0.27, 0.67) for the fasting plasma total AR concentration, suggesting moderate reproducibility. Fasting plasma total AR moderately correlated with WG rye + wheat (r(s) = 0.53; P < 0.001) and cereal fiber intake (r(s) = 0.32; P < 0.05) when using mean values from both occasions. This suggests that plasma AR concentration in fasting samples can be used as a biomarker of rye + wheat WG intake in free-living populations with a high and consistent WG intake.