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American Journal of Clinical Nutrition, Vol. 84, No. 4, 835-842, October 2006
© 2006 American Society for Nutrition

ORIGINAL RESEARCH COMMUNICATION

Postprandial metabolic fate of tocotrienol-rich vitamin E differs significantly from that of {alpha}-tocopherol1,2,3

Syed Fairus1, Rosnah M Nor1, Hwee M Cheng1 and Kalyana Sundram1

1 From the Food Technology and Nutrition Unit, Malaysian Palm Oil Board, Selangor, Malaysia (SF, RMN, and KS), and the Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia (HMC)

Background: The detection of tocotrienols in human plasma has proven elusive, and it is hypothesized that they are rapidly assimilated and redistributed in various mammalian tissues.

Objective: The primary study objective was to evaluate the postprandial fate of tocotrienols and {alpha}-tocopherol in human plasma and lipoproteins.

Design: Seven healthy volunteers (4 males, 3 females) were administered a single dose of vitamin E [1011 mg palm tocotrienol-rich fraction (TRF) or 1074 mg {alpha}-tocopherol] after a 7-d conditioning period with a tocotrienol-free diet. Blood was sampled at baseline (fasted) and 2, 4, 5, 6, 8, and 24 h after supplementation. Concentrations of tocopherol and tocotrienol isomers in plasma, triacylglycerol-rich particles (TRPs), LDLs, and HDLs were measured at each interval.

Results: After intervention with TRF, plasma tocotrienols peaked at 4 h (4.79 ± 1.2 µg/mL), whereas {alpha}-tocopherol peaked at 6 h (13.46 ± 1.68 µg/mL). Although tocotrienols were similarly detected in TRPs, LDLs, and HDLs, tocotrienol concentrations were significantly lower than {alpha}-tocopherol concentrations. In comparison, plasma {alpha}-tocopherol peaked at 8 h (24.3 ± 5.22 µg/mL) during the {alpha}-tocopherol treatment and emerged as the major vitamin E isomer detected in plasma and lipoproteins during both the TRF and the {alpha}-tocopherol treatments.

Conclusions: Tocotrienols are detected in postprandial plasma, albeit in significantly lower concentrations than is {alpha}-tocopherol. This finding confirms previous observations that, in the fasted state, tocotrienols are not detected in plasma. Tocotrienol transport in lipoproteins appears to follow complex biochemically mediated pathways within the lipoprotein cascade.

Key Words: Tocotrienols • tocopherols • vitamin E • postprandial plasma






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