So, Why do People Say that Bananas Make You Happier? Bananas contain tryptophan, an amino acid, that the body converts into serotonin. It is serotonin that is responsible for making people feel happier. Serotonin, also known as the “happy hormone”, promotes a more positive, happy mood. Eating bananas will lead to increased levels of serotonin, which ultimately may make you feel more upbeat and happy.