What Exactly Is Serotonin? Serotonin is one of those brain chemicals that gets talked about a lot—and for good reason. It plays a big role in steadying your mood and helping you sleep better. Researchers have found that serotonin levels can affect how you feel and even how you behave, and it’s often linked to both feeling happier and living a longer, healthier life. The good news? You don’t need a prescription to give your serotonin a natural lift. Two of the most effective ways are through diet and exercise. And when it comes to food, the key is something…