Two fatty acids are essential: linoleic (omega-6) and α-linolenic acid (omega-3). This means that we need them to survive and must get them with food.
Omega-6 and omega-3 fatty acids are key for the proper functioning of the body, but they need to be present in the correct ratio. Both types of fatty acids in the body compete for the same enzymes, which transform them into biologically-active compounds.
If more omega-6 fatty acids are present in the body, the body will use proportionally more enzymes to transform them, which leads to inflammation. The recommended ratio for the intake of omega-6 and omega-3 fatty acids is 5:1. This means that omega-6 fatty acids should represent 2.5% and omega-3 fatty acids 0.5% of your daily energy intake.
Omega-6 and omega-3 fatty acids are often present together in foods. Many foods that are a good source of omega-3 are often an even richer source of omega-6. Consequently, the ratio of consumed omega-6 and omega-3 fatty acids for most people is much higher than 5:1, going as high as 20:1 and beyond. A classic example of such a food are walnuts. Walnuts contain lots of omega-3 fatty acids, but they are even richer with omega-6 fatty acids. The ratio is 4:1.