Ionizing radiation even at low doses can lead to lethal effects. Sustained exposure may even increase the risk of cancer in the long-term. Radiation exposure induces free radical species which mediates many of the acute and chronic effects of ionizing radiation. Increased reactive oxygen species following ionizing radiation exposure can empty antioxidant stores, cause cell death in tissues and hastens the ageing process. 
Tocotrienol emerging radioprotective effects
Gamma-tocotrienol potently reduces the expression of GFRP, one of the key regulatory proteins in the tetrahydrobiopterin (BH4) pathway, and may thus exert some of its beneficial effects on post-radiation free radical production partly by counteracting the decrease in BH4.  BH4 is known to reduce post-irradiation vascular oxidative stress.
Tocotrienol stimulates blood cell production, protects against radiation-induced cell death and promotes cellular protective mechanisms. Results from this study suggest that tocotrienol may improve survival following irradiation by enhancing blood cell production in the bone marrow and modulating signalling pathways. 
In vivo animal studies, including a number of published studies by researchers from the U.S. Armed Forces Radiobiology Research Institute (AFRRI) at the Uniformed Services University of the Health Sciences, show that gamma- and delta-tocotrienols are able to provide good recovery and survivability for mice exposed to high doses of total body irradiation. [4,5] Their studies also showed that gamma- and delta-tocotrienols were able to protect the haematopoietic stem cells that produce all types of blood cells by preventing DNA damage. Other researchers also showed in animal studies that gamma-tocotrienol protects against gastrointestinal and vascular injury from total-body irradiation. 
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1. Epperly MW, et al. Antioxidant-chemoprevention diet ameliorates late effects of total-body irradiation and supplements radioprotection by MnSOD-plasmid liposome administration. Radiat Res, 2011. 175(6): 759-65.
2. Berbee M, et al. Reduction of radiation-induced vascular nitrosative stress by the vitamin E analog gamma-tocotrienol: evidence of a role for tetrahydrobiopterin. Int J Radiat Oncol Biol Phys, 2011. 79(3): 884-91.
4. Satyamitra MM, Kulkarni S, Ghosh SP, et al. Hematopoietic Recovery and Amelioration of Radiation-Induced Lethality by the Vitamin E Isoform δ-Tocotrienol. Radiat Res 2011. (Epub Ahead of Print)
5. Berbee M, Fu Q, Boerma M, Wang J, Kumar KS and Hauer-Jensen M. Gamma-Tocotrienol ameliorates intestinal radiation injury and reduces vascular oxidative stress after total-body irradiation by an HMG-CoA reductase-dependent mechanism. Radiat Res 2009;171(5):596-605.