Whole-grain rye bread consumption by women correlates with plasma alkylresorcinols and increases their concentration compared with low-fiber wheat bread

Whole-grain rye and wheat products are rich in lignans, the precursors of enterolactone (ENL) and alkylresorcinols (ARs), which are phenolic lipids. In this crossover trial, we examined the effect of whole-grain rye bread compared with low-fiber wheat bread on plasma AR levels. Women (n = 39) aged 59 ± 0.94 y (mean ± SEM) were advised to consume rye (214 ± 7.1 g/d) or wheat (178 ± 6.5 g/d) bread (20% of total daily energy intake) in random order for 8 wk. The test periods were separated by an 8-wk washout period. ARs with different homologues and ENL were measured in plasma collected at the beginning (habitual diet) and end of the test bread periods. AR concentrations were higher (P < 0.001) after the rye bread (352 ± 24.7 nmol/L) and habitual diet (97.7 ± 12.1 and 88.3 ± 8.7 nmol/L) periods than after the wheat bread period (36.6 ± 4.2 nmol/L). Plasma AR concentrations were correlated with intake of rye bread (r = 0.34, P = 0.037), and with insoluble fiber from the whole diet during the rye (r = 0.39, P = 0.013) and wheat (r = 0.32, P = 0.047) bread periods. The plasma AR 17:0/21:0 ratio differed after the rye (0.84 ± 0.04) and wheat (0.53 ± 0.08) bread diet periods (P < 0.001). These data strongly suggest that plasma ARs could be used as specific biomarkers for whole-grain rye intake, and their homologue pattern could be used as an indicator of the bread type consumed.