A 2011 study in Nature Neuroscience has even demonstrated how lower omega-3 levels change brain activity, according to Eating Well. Other studies have shown that omega-3s appear to help maintain healthy levels of the brain chemicals dopamine and serotonin. Take a high-concentration fish oil supplement (1,050 mg of EPA and 150 mg of DHA), or eat oily, fatty fish (mackerel, herring, salmon, sardines, anchovies). You could also go with flaxseeds and walnuts. It's easy to incorporate flaxseed meal in your hot and cold cereals and smoothies, and you can use it as a substitute when you're baking and out of eggs (or you're a vegan). Try this Viva Naturals Organic Ground Flaxseed. Price: $8.99.