4. Go fish
Research from the National Institutes of Health shows that the omega-3 fatty acids in fish can significantly raise your levels of serotonin, a mood-boosting brain chemical. Of the 10 most common types of fish eaten in the U.S., salmon supplies the highest levels of omega-3 fatty acids.
Aim to get two 4-ounce servings of salmon or another fatty fish, like halibut or canned light tuna, every week. One way to work it into your diet: Top field greens with sliced salmon and walnuts (one of the few nonfish sources of omega-3s) and toss in a vinaigrette made with canola or olive oil. "Avoid using a lot of soybean and sunflower oils," adds Janice Kiecolt-Glaser, Ph.D., a professor of psychiatry at Ohio State University Medical Center in Columbus. "They contain high levels of omega-6 fatty acids, which will undo some of the benefits of omega-3s."
5. Curb the coffee
Because caffeine stimulates the central nervous system, getting too much can make you restless and jittery. Instead of your morning mug of joe or afternoon cola, brew a cup of green tea. Not only does it have less caffeine, it contains L-theanine, an amino acid Japanese researchers say has a calming effect on the brain.
6. Put on a happy face
Making yourself smile—a real smile, using not just your lips but also the muscles around your eyes—can activate feel-good parts of the brain, finds a study from the University of California, San Francisco. Need help turning that frown upside down? Meet up with your most cheerful friend. "Studies show we mimic the emotions of the person we're interacting with," says Elaine Hatfield, Ph.D., a psychology professor at the University of Hawaii and co-author of Emotional Contagion.
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