If you take just one supplement to boost your brain health, make it fish oil! One of the purer brands is Carlson's. It takes several pills to equal one tablespoon of fish oil, so I recommend using the liquid. It is expensive (about $50 per large bottle) but lasts a long time.
Vegetarians: Flax seed oil is helpful but is not as beneficial as fish oil.
Here is an article that provides more info:
JoAnne McFarland O'Rourke