> Diets low in omega-3 fatty acids, found in seafood [...] also played a role.

In seafood you also find a lot of toxins, especially mercury. So trying to get your omega3s from there comes with it's own problems.

Thank God for flax seeds! A cheap and pure source of omega3s. Freshly grind 2 tsps and mix in your food every day: you will have covered your omega3s, amongst other micro-nutrients.