Omega-6 fatty acids and inflammation

•There is a high content of omega-6 PUFAs, particularly arachidonic acid, in membranes of cells involved in inflammation.•High omega-6 PUFA dietary intake has been linked to inflammation, mainly because ARA is the precursor of pro-inflammatory lipid mediators.•However, some studies have shown that increased dietary intake of omega-6 PUFAs may not lead to enhanced inflammation.•This article investigates the extent to which omega-6 PUFAs are involved in the inflammatory process. Inflammation is a normal process that is part of host defence and tissue healing. However, excessive or unresolved inflammation can lead to uncontrolled tissue damage, pathology and disease. In humans on a Western diet, the omega-6 polyunsaturated fatty acid arachidonic acid (ARA) makes a significant contribution to the fatty acids present in the membrane phospholipids of cells involved in inflammation. ARA is a precursor to a number of potent pro-inflammatory mediators including well described prostaglandins and leukotrienes, which has led to the development of anti-inflammatory pharmaceuticals that target the ARA pathway to successfully control inflammation. Hence, it is commonly believed that increasing dietary intake of the omega-6 fatty acids ARA or its precursor linoleic acid (LA) will increase inflammation. However, studies in healthy human adults have found that increased intake of ARA or LA does not increase the concentrations of many inflammatory markers. Epidemiological studies have even suggested that ARA and LA may be linked to reduced inflammation. Contrastingly, there is also evidence that a high omega-6 fatty acid diet inhibits the anti-inflammatory and inflammation-resolving effect of the omega-3 fatty acids. Thus, the interaction of omega-3 and omega-6 fatty acids and their lipid mediators in the context of inflammation is complex and still not properly understood.