Serotonin is a feel good neurotransmitter produced mainly in the gastrointestinal GI tract. Its thought to have a strong influence on mood, appetite and digestion.
Eating carbohydrates and sugar increases the release of serotonin making us feel fabulous temporarily. So when our levels are low our brains think “Oh! that candy bar or bagel is going to fix this!”
A low serotonin level can be due to a variety of things including poor gut health.