High concentrations of enterolignans in plasma are associated with a lower risk of acute coronary events. However, little is known about the absorption and excretion of enterolignans. The pharmacokinetic parameters and urinary excretion of enterodiol and enterolactone were evaluated after consumption of their purified plant precursor, secoisolariciresinol diglucoside (SDG). Twelve healthy volunteers ingested a single dose of purified SDG (1.31 micromol/kg body wt). Enterolignans appeared in plasma 8-10 h after ingestion of the purified SDG. Enterodiol reached its maximum plasma concentration 14.8 +/- 5.1 h (mean +/- SD) after ingestion of SDG, whereas enterolactone reached its maximum 19.7 +/- 6.2 h after ingestion. The mean elimination half-life of enterodiol (4.4 +/- 1.3 h) was shorter than that of enterolactone (12.6 +/- 5.6 h). The mean area under the curve of enterolactone (1762 +/- 1117 nmol/L . h) was twice as large as that of enterodiol (966 +/- 639 nmol/L . h). The mean residence time for enterodiol was 20.6 +/- 5.9 h and that for enterolactone was 35.8 +/- 10.6 h. Within 3 d, up to 40% of the ingested SDG was excreted as enterolignans via urine, with the majority (58%) as enterolactone. In conclusion, a substantial part of enterolignans becomes available in the blood circulation and is subsequently excreted. The measured mean residence times and elimination half-lives indicate that enterolignans accumulate in plasma when consumed 2-3 times a day and reach steady state. Therefore, plasma enterolignan concentrations are expected to be good biomarkers of dietary lignan exposure and can be used to evaluate the effects of lignans.