If you’re looking for a happiness boost: Eat blueberries. According to the journal Pharmacological Research, eating a half-cup of blueberries every day could raise your serotonin levels by 20%. Serotonin is a brain chemical linked to a better mood. It also helps keep your brain cells and arteries running smoothly – decreasing the risk of stroke, heart disease and Alzheimer’s. And we get the serotonin boost from the anthocyanin in blueberries; the antioxidant that gives them their deep color.