Vitamin E is a fat-soluble compound and powerful antioxidant that have been shown to protect the cell membranes against damage caused by free radicals. Human vitamin E supplementation studies are usually limited to α-tocopherol but currently tocotrienols are also available. This study aims to compare the effects of tocotrienol rich fraction (TRF) with α-tocopherol (α-TF) supplementation on oxidative stress in healthy male and female older adults aged 50-55 years old. A total of 71 subjects both male and female aged between 50 and 55 years were divided into groups receiving placebo (n = 23), α-TF (n = 24) and TRF (n = 24) for six months. Blood was taken at baseline (month 0), 3 months and 6 months osf supplementation for determination of plasma malondialdehyde (MDA), protein carbonyl, total DNA damage, vitamin D concentration and vitamin E isomers. α-TF supplementation reduced plasma MDA and protein carbonyl in female subjects after 3 and 6 months. TRF supplementation reduced MDA levels in both males and females as early as 3 months while DNA damage was reduced in females only at 6 months. Supplementation with α-TF and TRF increased plasma vitamin D concentration in both males and females after 6 months, but vitamin D concentration in male subjects were significantly higher compared to female subjects in TRF group. Vitamin E isomer determination showed α-TF, α-tocotrienol and γ-tocotrienol were increased in both male and female subjects. In conclusion, TRF supplementation effects were different from α-TF in reducing oxidative stress markers and vitamin D levels with a more pronounced effect in female subjects.
A single dose comparative bioavailability study was conducted to evaluate the bioavailability of tocotrienols from two self-emulsifying formulations, one of which produced an emulsion that readily lipolysed under in vitro condition (SES-A), while the other produced a finer dispersion with negligible lipolysis (SES-B) in comparison with that of a non-self-emulsifying formulation in soya oil. The study was conducted according to a three-way crossover design using six healthy human volunteers. Statistically significant differences were observed between the logarithmic transformed peak plasma concentration (Cmax) and total area under the plasma concentration-time curve (AUC(0-infinity)) values of both SES-A and -B compared to NSES-C indicating that SES-A and -B achieved a higher extent of absorption compared to NSES-C. Moreover, the 90% confidence interval of the AUC(0-infinity) values of both SES-A and -B over those of NSES-C were between 2-3 suggesting an increase in bioavailability of about two-three times compared to NSES-C. Both SES-A and -B also achieved a faster onset of absorption. However, both SES-A and -B had comparable bioavailability, despite the fact that SES-B was able to form emulsions with smaller droplet size. Thus, it appeared that both droplet sizes as well as the rate and extent of lipolysis of the emulsion products formed were important for enhancing the bioavailability of the tocotrienols from the self-emulsifying systems.