The reason the answer isn’t clear is because the studies have had their subjects taking placebo doses of omega-3 fatty acids. The secret of omega-3 fatty acids is that they are substrates for hormones (resolvins) needed to resolve existing inflammation. Until you get the AA/EPA ratio under 3, then you are not going to see any benefit of omega-3 fatty acids. The average AA/EPA ratio for Japanese is 1.5 to 3 compared to the average American who has an AA/EPA ratio of 18. To get the same AA/EPA ratio as the Japanese will require about 5 to 7.5 grams of EPA and DHA per day.
Omega-3s are the fats that made fish famous. Really famous: fish oil is now the most popular natural product in America among U.S. adults-8% of whom take it-and children. Our bodies need these essential unsaturated fats but can’t produce them, so we rely on sources like seafood or supplements to get enough.