Research

Alpha-tocotrienol is the most abundant tocotrienol isomer circulated in plasma and lipoproteins after postprandial tocotrienol-rich vitamin E supplementation

Syed Fairus, Rosnah M Nor, Hwee M Cheng and Kalyana Sundram

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Nutrition Journal 2012, 11:5 doi:10.1186/1475-2891-11-5

Published: 17 January 2012

Abstract (provisional)

Background

Tocotrienols (T3) and tocopherols (T), both members of the natural vitamin E family have unique biological functions in humans. T3 are detected in circulating human plasma and lipoproteins, although at concentrations significantly lower than alpha-tocopherol (alpha-T). T3, especially alpha-T3 is known to be neuropotective at nanomolar concentrations and this study evaluated the postprandial fate of T3 and alpha-T in plasma and lipoproteins.

Methods

Ten healthy volunteers (5 males and 5 females) were administered a single dose of vitamin E [526 mg palm tocotrienol-rich fraction (TRF) or 537 mg alpha-T] after 7-d pre-conditioning on a T3-free diet. Blood was sampled at baseline (fasted) and 2, 4, 5, 6, 8, and 24 h after supplementation. Concentrations of T and T3 isomers in plasma, triacylglycerol-rich particles (TRP), LDL, and HDL were measured at each postprandial interval.

Results

After TRF supplementation, plasma alpha-T3 and gamma-T3 peaked at 5 h (alpha-T3: 4.74 +/- 1.69 uM; gamma-T3: 2.73 +/- 1.27 uM). delta-T3 peaked earlier at 4 h (0.53 +/- 0.25 uM). In contrast, alpha-T peaked at 6 h (30.13 +/- 2.91 uM) and 8 h (37.80 +/- 3.59 uM) following supplementation with TRF and alpha-T, respectively. alpha-T was the major vitamin E isomer detected in plasma, TRP, LDL, and HDL even after supplementation with TRF (composed of 70% T3). No T3 were detected during fasted states. T3 are detected postprandially only after TRF supplementation and concentrations were significantly lower than alpha-T.

Conclusions

Bio-discrimination between vitamin E isomers in humans reduces the rate of T3 absorption and affects their incorporation into lipoproteins. Although low absorption of T3 into circulation may impact some of their physiological functions in humans, T3 have biological functions well below concentration noted in this study.