ABSTRACT: Background: Vitamin E supplementation improves liver histology in patients with nonalcoholic steatohepatitis, which is a manifestation of the metabolic syndrome (MetS). We reported previously that ?-tocopherol bioavailability in healthy adults is higher than in those with MetS, thereby suggesting that the latter group has increased requirements.Objective: We hypothesized that ?-tocopherol catabolites ?-carboxyethyl hydroxychromanol (?-CEHC) and ?-carboxymethylbutyl hydroxychromanol (?-CMBHC) are useful biomarkers of ?-tocopherol status.Design: Adults (healthy or with MetS; n = 10/group) completed a double-blind, crossover clinical trial with four 72-h interventions during which they co-ingested 15 mg hexadeuterium-labeled RRR-?-tocopherol (d6-?-T) with nonfat, reduced-fat, whole, or soy milk. During each intervention, we measured ?-CEHC and ?-CMBHC excretions in three 8-h urine collections (0-24 h) and plasma ?-tocopherol, ?-CEHC, and ?-CMBHC concentrations at various times ?72 h.Results: During the first 24 h, participants with MetS compared with healthy adults excreted 41% less ?-CEHC (all values are least-squares means ± SEMs: 0.6 ± 0.1 compared with 1.0 ± 0.1 ?mol/g creatinine, respectively; P = 0.002), 63% less hexadeuterium-labeled (d6)-?-CEHC (0.04 ± 0.02 compared with 0.13 ± 0.02 ?mol/g creatinine, respectively; P = 0.002), and 58% less d6-?-CMBHC (0.017 ± 0.004 compared with 0.041 ± 0.004 ?mol/g creatinine, respectively; P = 0.0009) and had 52% lower plasma d6-?-CEHC areas under the concentration curves [area under the curve from 0 to 24 h (AUC0-24h): 27.7 ± 7.9 compared with 58.4 ± 7.9 nmol/L × h, respectively; P = 0.01]. d6-?-CEHC peaked before d6-?-T in 77 of 80 paired plasma concentration curves. Urinary d6-?-CEHC 24-h concentrations were associated with the plasma AUC0-24 h of d6-?-T (r = 0.53, P = 0.02) and d6-?-CEHC (r = 0.72, P = 0.0003), and with urinary d6-?-CMBHC (r = 0.88, P < 0.0001), and inversely with the plasma inflammation biomarkers C-reactive protein (r = -0.70, P = 0.0006), interleukin-10 (r = -0.59, P = 0.007), and interleukin-6 (r = -0.54, P = 0.01).Conclusion: Urinary ?-CEHC and ?-CMBHC are useful biomarkers to noninvasively assess ?-tocopherol adequacy, especially in populations with MetS-associated hepatic dysfunction that likely impairs ?-tocopherol trafficking. This trial was registered at clinicaltrials.gov as NCT01787591.