Omega 3 essential fatty acids are found in fish, flaxseed oil, and walnuts. As opposed to omega 6 essential fatty acid found in extra virgin olive oil for example, omega 3 has an anti inflammatory effect in the body. Unfortunately, we get 20 times as much omega 6 as we do omega 3 (because we aren't primitive natives). Ideally we should be getting four parts omega 6 to one part omega 3.
If everyone made sure that this was the case, then a lot of cases of heart disease, attention disorders, learning disabilities and allergies would be prevented.