Epidemiological data suggest a link between fat quality (i.e. types of fatty acids consumed) and cancer. Animal experiments have shown that the polyunsaturated fatty acids (PUFA), especially those of the n-6 series derived from vegetable seed oils, have tumor promoting effects in mammary cancer models. Thus the fatty acids of palm oil attracted initial attention with regards to their ability to inhibit and/or delay experimental carcinogenesis. It was shown almost 15 years ago that palm oil did not promote mammary carcinogenesis in a rat model, primarily because it contained far less PUFA than corn oil.
Attention then shifted to the vitamin E content of
palm oil when its was noted that palm oil stripped of its vitamin E content - promoted mammary carcinogenesis - just like other unsaturated fatty acid rich lipids. Furthermore, when the vitamin E fraction from palm oil was added back to a polyunsaturated fatty acid-enriched diet, the "cancer" was inhibited. The vitamin E of palm oil, consists largely of tocotrienols, the remainder being a-tocopherol. (This fraction of palm oil is referred to as the tocotrienol-rich fraction (TRF) or Palm Vitee). TRF has been subsequently shown to inhibit the proliferation and growth of human breast cancer cells in vitro, whereas a-tocopherol was ineffective. The individual tocotrienols from the TRF were also found to inhibit the cancer cells. In a direct comparison between the individual isomers of tocopherols and tocotrienols, it was shown that the tocotrienols were more effective than the tocopherols.
Since these early studies there is now a reasonable and ever-growing body of scientific literature documenting the anti-cancer properties of the tocotrienols. Although various mechanisms have been postulated for how tocotrienols exert their effect (including their role in apoptosis) - the exact mechanism has yet to be detailed. Recent reports suggests that TRF's ability to inhibit cancer cell growth and promote apoptosis may be mediated via signaling pathways (e.g. caspase-8, p53). For a more detailed review of the anticancer properties of palm oil - please see (Sambanthamurthi et al, 2000)
References
2) Kritchevsky, D., Weber, M. M. and Klurfeld, D. M. (1992) Influence of different fats (soybean oil, palm olein or hydrogenated soybean oil) on chemically-induced mammary tumors in rats. Nutr. Res. 12: S175-A179.
3) Nesaretnam, K., Khor, H. T., Ganeson, J., Chong, Y. H., Sundram, K. and Gapor, A. (1992) The effect of vitamin E tocotrienols from palm oil on chemically-induced mammary carcinogenesis in female rats. Nutr. Res. 12: 63-75.
4) Carroll, K. K., Guthries, N., Neseratnam, K., Gapor, A. and Chambers, A. F. (1995) Anti-cancer properties of tocotrienols from palm oil. In: Nutrition, Lipids, Health and Disease (Ong, A. S. H., Niki, E. and Packer, L., eds.), pp117-121. AOCS Press, Champaign, IL.
Thank you for this important information about tocotrienols and cancer prevention.
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