1. An omelet—just don't skip the yolk
Eat it for: The B vitamins and protein. Egg yolks are the vitamin-B-rich part of the egg.
Other examples: Lean beef, wheat germ, fish, poultry
A 2010 study of 3,000 older adults followed over 12 years found that those with lower intake of these vitamins had a higher risk of depression, according to the American Journal of Clinical Nutrition.
2. Nuts and seed:Eat it for: The magnesium
Examples: Pumpkin seeds, sunflower seeds, cashews, almonds, peanuts. (Green leafy vegetables and whole grains are also high in magnesium.)
Magnesium, a mineral found naturally in nuts and seeds, influences production of serotonin, a "feel-good" brain chemical.
3. Cold-water fish
Eat it for: The omega-3 fatty acids
Examples: Wild salmon, herring, sardines, anchovies, tuna (not more than once per week), rainbow trout, mackerel.
There's a reason fish is known as "brain food." Fatty fish such as wild salmon contain the omega-3 fatty acid DHA, which has been shown to increase the membrane quality and nerve function of gray matter in the brain.
4. Ancient grains
Eat it for: The complex carbohydrates
Examples: Quinoa, millet, teff, amaranth, spelt, barley
5. Green tea
Drink it for: The amino acid L-theanine
Examples: Hot green tea, brewed iced green tea—including flavored varieties like jasmine green tea or berry green tea
"Despite the caffeine, the L-theanine in green tea seems to be profoundly relaxing, with effects that last up to eight hours," Reardon says. L-theanine is easily absorbed and can cross the blood-brain barrier, adding to its effectiveness.