Arachidonic acid is a precursor for thromboxane A2 which promotes platelet aggregation and increases fibrinogen levels as part of the clotting cascade.
DHA has anti-inflammatory effects and has been shown to reduce fibrinogen levels, likely by reducing inflammation that triggers clotting.
References
Mori T, Oikawa S, Hiroshima M, Matsuzaki M, Yokoyama M, Hashimoto M, Kobayashi J, Yoshida H, Kondo K. Effect of varying the ratio of n−6 to n−3 fatty acids by increasing the intake of eicosapentaenoic acid and docosahexaenoic acid in patients with hypertriglyceridemia. Atherosclerosis (2023). https://www.sciencedirect.com/science/article/pii/S0002916523290504Liu C, Ralston N. Omega-3 Polyunsaturated Fatty Acid (Fish Oil) Supplementation and the Cardiovascular System. Advances in Food and Nutrition Research (2021). https://www.ahajournals.org/doi/10.1161/CIR.0000000000000482Superko HR, Superko SM, Nasir K, Agatston A, Garrett BC. Do elevated blood levels of omega-3 fatty acids modify effects of particulate air pollutants on fibrinogen?. Current Opinion in Clinical Nutrition & Metabolic Care (2018). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6097058/Gao L, Zhao Y, Wang J, Wang Y, Wang J, Wang Y, Zhang J. Long-term influence of omega-3 fatty acids on fibrinolysis, fibrinogen, and serum lipids. Journal of Clinical Laboratory Analysis (2015). https://onlinelibrary.wiley.com/doi/abs/10.1002/jcla.21628
EPA, like DHA, has anti-inflammatory properties and has been found to lower fibrinogen concentrations, possibly by a similar mechanism of reducing inflammation.
Palmitic acid may increase fibrinogen production in the liver by activating inflammatory pathways and increasing expression of the fibrinogen gene.
References
R. T. Murray, P. R. Clarke, J. R. Vane. Fatty acids, fibrinogen and blood flow: A general mechanism for … Thrombosis and Haemostasis (1980). https://www.sciencedirect.com/science/article/pii/0306987780901085J. E. M. Thijs, M. C. M. W. van Herpen-Broekmans, H. P. J. Lemmens, W. J. van der Kuip, D. Kocks, J. C. Jukema, J. W. Jukema, P. J. Koudstaal, F. G. R. F. H. Rabelink, J. Jukema. Association of the Fatty Acid Composition of Serum … Arteriosclerosis, Thrombosis, and Vascular Biology (2000). https://www.ahajournals.org/doi/full/10.1161/01.atv.17.5.809L. P. C. van Oostrom, M. A. J. van den Berg, M. C. M. W. van Herpen-Broekmans, J. E. M. Thijs, E. J. M. Feskens, R. J. F. Nijmegen. Implication of Free Fatty Acids in Thrombin Generation and … Nutrients (2017). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5702631/J. L. Vega-López, M. Rangel-Huerta, A. A. Pérez-Martínez, J. M. de la Rosa, M. A. López-Miranda, E. Martínez-González, R. Sánchez-Villegas. Ratio of oleic to palmitic acid is a dietary determinant of … Atherosclerosis (2023). https://www.sciencedirect.com/science/article/pii/S0002916523290152
Stearic acid is a saturated fatty acid that may contribute to inflammation and increased fibrinogen synthesis, similar to the effects of palmitic acid.