(25-01-14) Bioavailability of tocotrienols: evidence in human studies

Ju-Yen Fu14*, Hui-Ling Che12, Doryn Meam-Yee Tan13 and Kim-Tiu Teng1

* Corresponding author: Ju-Yen Fu [email protected]

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Abstract

As a minor component of vitamin E, tocotrienols were evident in exhibiting
biological activities such as neuroprotection, radio-protection,
anti-cancer, anti-inflammatory and lipid lowering properties which are not
shared by tocopherols. However, available data on the therapeutic window of
tocotrienols remains controversial. It is important to understand the
absorption and bioavailability mechanisms before conducting in-depth
investigations into the therapeutic efficacy of tocotrienols in humans. In
this review, we updated current evidence on the bioavailability of
tocotrienols from human studies. Available data from five studies suggested
that tocotrienols may reach its target destination through an alternative
pathway despite its low affinity for á-tocopherol transfer protein. This was
evident when studies reported considerable amount of tocotrienols detected
in HDL particles and adipose tissues after oral consumption. Besides, plasma
concentrations of tocotrienols were shown to be higher when administered
with food while self-emulsifying preparation of tocotrienols was shown to
enhance the absorption of tocotrienols. Nevertheless, mixed results were
observed based on the outcome from 24 clinical studies, focusing on the
dosages, study populations and formulations used. This may be due to the
variation of compositions and dosages of tocotrienols used, suggesting a
need to understand the formulation of tocotrienols in the study design.
Essentially, implementation of a control diet such as AHA Step 1 diet may
influence the study outcomes, especially in hypercholesterolemic subjects
when lipid profile might be modified due to synergistic interaction between
tocotrienols and control diet. We also found that the bioavailability of
tocotrienols were inconsistent in different target populations, from healthy
subjects to smokers and diseased patients. In this review, the effect of
dosage, composition and formulation of tocotrienols as well as study
populations on the bioavailability of tocotrienols will be discussed.


Source: Nutrition & Metabolism 2014, 11:5 doi:10.1186/1743-7075-11-5
Published: 13 January 2014

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