Fatty acid facts, part II: role in the prevention of carcinogenesis, or, more fish on the dish?

Many laboratory studies suggest that n-3 fatty acids, especially the long-chain polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have antitumor effects. The mechanisms involved in their anticarcinogenic action include the suppression of the biosynthesis of proinflammatory molecules, the influence on transcription factor activity and gene expression, the influence on signal transduction, the alteration of hormone-stimulated cell growth and the suppression of the production of free radicals and reactive oxygen species. In general, n-6 fatty acids and their derivatives promote the production of proinflammatory eicosanoids, whereas n-3 fatty acids suppress this action. The encouraging preclinical results are only scarcely confirmed in reviews and meta-analysis of epidemiological data roughly published before 2005. However, around 2005, the first reports on epidemiological studies based on the assessment of the concentration of EPA and DHA in the erythrocyte cell membrane in individual study participants started to appear. Without exception, these publications demonstrate that higher EPA (and possibly DHA) concentrations in the cell membrane, a validated measure for plasma fatty acids, is associated with lower cancer risk. These intriguing results are confirmed by the recently published huge European Prospective Investigation into cancer and nutrition (N = 478,040 men and women) and U.S.-based Physicians Health Study (N = 22,071 men). These studies have unequivocally confirmed that fish intake has a favorable effect on cancer risk . This review aims to elucidate the various mechanisms by which n-3 fatty acids may affect the process of carcinogenesis. For this summary of knowledge, we focus on the effects of n-3 intake on the risk of breast cancer, prostate cancer and colorectal cancer. Copyright 2008 Prous Science, S.A.U. or its licensors. All rights reserved.