The cancer preventive activity of vitamin E has been documented in epidemiological studies, but large-scale prevention trials using alpha tocopherol have proved disappointing.14 Consequently, recent studies have begun to focus on the other vitamin E forms (isomers), including gamma tocopherol, delta tocopherol and the tocotrienols. These studies provide strong evidence that gamma tocopherol, the principal form of vitamin E in the diet,15 and delta tocopherol activate Nrf2 and NF-kΒ signalling pathways more effectively than alpha tocopherol, the principal form of vitamin E found in supplements.16 As well, gamma tocotrienol has been found to block NF-kΒ levels and enhance Nrf2 levels to a greater extent than alpha tocopherol.17
In a recent study, a gamma tocopherol-rich mixture of vitamin E stimulated a strong Nrf2-dependent antioxidant response, with the consequent downstream manufacture of the endogenous antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase.18 Gamma tocopherol has also been shown to induce a significant increase in cellular glutathione levels while alpha tocopherol did not.19 Moreover, gamma tocopherol demonstrated greater anti-inflammatory and anti-tumor activity in several animal models of cancer than did alpha tocopherol. The gamma form of vitamin E has also been shown to effectively inhibit cell proliferation, up-regulate Nrf2 expression, and suppress inflammatory molecules.20
The tocotrienols belong to the vitamin E family and have also been shown to exhibit potent protective effects against aberrant cell growth.21;22 In human breast cancer studies a mixture of alpha, delta, and gamma tocotrienols led to a several-fold increase in Nrf2 expression, indicating a strong upregulation of cytoprotective endogenous antioxidant systems.22
Taken together, the evidence shows that gamma tocopherol, along with the mixed tocopherols and tocotrienols─in preference to alpha tocopherol—play an important role in the regulation of cellular antioxidant signalling pathways.
NutriSearch Corporation is a Canadian company specializing in nutrition and health research, focussed primarily on multiple vitamin and mineral supplementation.
Our main product is the NutriSearch Comparative Guide to Nutritional Supplements™, which examines current research on the health benefits of supplementation for prevention of degenerative disease. The guide also includes comparisons of broad-spectrum supplements available in various markets around the world, is available in various regions. The guide for the Americas includes product comparisons from Canada, Colombia, México, and the United States. We also publish a guide for Australia and New Zealand.
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