"The recommended n-6:n-3 ratio ranges from 1:1 to 4:1 in order to avoid adverse effects on metabolism. However, the Western diets provide ratios of between 10:1 and 20:1, and there are reports of 50:1 (Ratnayake & Galli, 2009). "
"The first step in the pathway requires Δ6 Desaturase   which has a higher affinity for ALA than LA but due to the typically higher intake and concentration of LA there is greater conversion of n-6 PUFA producing the predominant product of the n-6 pathway, arachidonic acid (AA or 20 : 4n-6) [1, 5–7]. Thus the capacity of human metabolism to derive EPA and DHA by the desaturation of ALA is negligible in normal circumstances . The efficiency of conversion is particularly poor in relation to DHA  . "
[Show abstract][Hide abstract] ABSTRACT: Omega-3 polyunsaturated fatty acids, in particular eicosapentaenoic acid, and docosahexaenoic acid have been shown to have multiple beneficial antitumour actions that affect the essential alterations that dictate malignant growth. In this review we explore the putative mechanisms of action of omega-3 polyunsaturated fatty acid in cancer protection in relation to self-sufficiency in growth signals, insensitivity to growth-inhibitory signals, apoptosis, limitless replicative potential, sustained angiogenesis, and tissue invasion, and how these will hopefully translate from bench to bedside.
"Two of the minor long-chain FA present in milk, α-linolenic acid (ALA; 18:3n-3) and linoleic acid (LeA; 18:2n-6) cannot be synthesized by cows because mammals are missing the desaturases that are needed to introduce double bonds at the Δ12 and Δ15 positions of FA (Arterburn et al., 2006). Therefore, ALA and LeA must be obtained from plant materials in the diet (Ratnayake and Galli, 2009). Mammals convert ALA and LeA metabolically into 2 different series of very long chain n-3 and n-6 FA by a single set of desaturases and elongases (Sprecher, 2002). "
[Show abstract][Hide abstract] ABSTRACT: Weekly samples representative of Dutch milk were analyzed for concentrations of n-3 and n-6 fatty acids (FA). Concentrations of the n-3 FA α-linolenic acid (ALA), eicosatetraenoic acid, eicosapentaenoic acid, and docosapentaenoic acid were 0.495 ± 0.027, 0.041 ± 0.004, 0.067 ± 0.005, and 0.086 ± 0.008 g per 100 g of fat, respectively, whereas docosahexaenoic acid was absent or present in concentrations lower than 0.020 g per 100 g of fat. Concentrations of the n-6 FA linoleic acid (LeA), γ-linoleic acid, dihomo-γ-linoleic acid, and arachidonic acid were 1.428 ± 0.068, 0.070 ± 0.007, 0.066 ± 0.004, and 0.089 ± 0.004 g per 100 g of fat, respectively; adrenic acid was present in concentrations lower than 0.020 g per 100 g of fat, whereas docosapentaenoic acid was absent in all samples. The concentrations of ALA and LeA were significantly higher in spring and summer, compared with autumn and winter. The concentrations of all other ALA- and LeA-derived n-3 and n-6 FA were not significantly different between seasons. The contribution of milk fat to the daily intake of eicosapentaenoic acid, docosapentaenoic acid and docosahexaenoic acid was calculated for human consumption levels in different countries. Milk fat contributed between 10.7 and 14.1% to the daily intake of eicosapentaenoic acid and between 23.5 and 34.2% to the intake of docosapentaenoic acid; whereas docosahexaenoic acid contribution was marginal. Arachidonic acid from milk fat contributed between 10.5 and 18.8% to the human intake of n-6 FA.
Note: This list is based on the publications in our database and might not be exhaustive.
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