[alpha]-Tocopherol bioavailability is lower in adults with metabolic syndrome regardless of dairy fat co-ingestion: a randomized, double-blind, crossover trial

Increasing dietary fat intake is expected to improve a-tocopherol bioavailability, which could be beneficial for improving a-tocopherol status, especially in cohorts at high cardiometabolic risk who fail to meet dietary a-tocopherol requirements. Our objective was to assess dose-dependent effects of dairy fat and metabolic syndrome (MetS) health status on a-tocopherol pharmacokinetics in plasma and lipoproteins. A randomized, crossover, double-blind study was conducted in healthy and MetS adults (n = 10/group) who ingested encapsulated hexadeuterium-labeled (d6)-RRR-a-tocopherol (15 mg) with 240 mL nonfat (0.2 g fat), reduced-fat (4.8 g fat), or whole (7.9 g fat) milk before blood collection at regular intervals for 72 h. Compared with healthy participants, those with MetS had lower (P < 0.05) baseline plasma a-tocopherol (μmol/mmol lipid) and greater oxidized low-density lipoprotein (LDL), interleukin (IL)-6, IL-10, and C-reactive protein. Regardless of health status, d6-a-tocopherol bioavailability was unaffected by increasing amounts of dairy fat provided by milk beverages, but MetS participants had lower estimated d6-a-tocopherol absorption (±SEM) than did healthy participants (26.1% ± 1.0% compared with 29.5% ± 1.1%). They also had lower plasma d6-a-tocopherol AUC from 0 to 72 h, as well as maximal concentrations (Cmax: 2.04 ± 0.14 compared with 2.73 ± 0.18 μmol/L) and slower rates of plasma disappearance but similar times to Cmax. MetS participants had lower d6-a-tocopherol AUC from t = 0-12 h (AUC0-t final) in lipoprotein fractions [chylomicron, very-low-density lipoprotein (VLDL), LDL, high-density lipoprotein]. Percentages of d6-a-tocopherol AUC0-t final in both the chylomicron (r = -0.46 to -0.52) and VLDL (r = -0.49 to -0.68) fractions were inversely correlated with oxidized LDL, IL-10, IL-6, and C-reactive protein. At dietary intakes equivalent to the Recommended Dietary Allowance, a-tocopherol bioavailability is unaffected by dairy fat quantity but is lower in MetS adults, potentially because of greater inflammation and oxidative stress that limits small intestinal a-tocopherol absorption and/or impairs hepatic a-tocopherol trafficking. These findings support higher dietary a-tocopherol requirements for MetS adults.