Co-Ingestion Timing, Rather than Food Matrix or Dose, Determines α-Tocopherol Bioavailability from Intrinsically Labeled Spinach in Healthy Adults: A Crossover Pharmacokinetic Study.

Dark green leafy vegetables, such as spinach, are rich sources of α-tocopherol (α-T), a lipid-soluble antioxidant, but may contribute little to α-T status due to low intake and limited bioavailability. This study investigated whether egg co-consumption enhances α-T bioavailability from spinach and whether effects differ by egg dose, food matrix, or timing of intake. In a crossover study, healthy adults consumed deuterium-labeled (dx)-spinach (containing 5 mg dx-α-T) alone; or with 1, 2, or 3 hard-boiled eggs; 2 egg whites; or vegetable oil (9.6 g). Two exploratory trials evaluated delayed egg consumption 3 h after spinach intake. Compared with spinach alone, dx-α-T AUC0-72h (µmol/L × h) was 1.5-1.8-times higher when spinach was co-consumed with 1, 2, and 3 eggs (p ≤ 0.05), respectively, with no egg dose-dependent differences (p > 0.05). Co-ingestion of spinach with egg whites or vegetable oil increased dx-α-T AUC0-72h similar to whole eggs (p > 0.05). Delayed egg intake did not affect dx-α-T AUC0-72h relative to spinach alone (p > 0.05). Plant-derived α-T bioavailability can be improved through co-ingestion with other foods but is independent of egg dose and food matrix. Effective absorption requires concurrent intake, indicating that timing and associated digestive processes are key determinants and support food-pairing strategies to improve vitamin E bioavailability and its antioxidant contribution to plant-based diets. Registered at ClinicalTrials.gov (NCT04287816).