L-tryptophan is an essential amino acid that the body cannot produce on its own, meaning it must be obtained through diet. It is found in various protein-rich foods such as turkey, chicken, fish, eggs, dairy products, nuts, and seeds. L-tryptophan plays a crucial role in the production of serotonin, a neurotransmitter that helps regulate mood, sleep, and appetite. In addition to its role in serotonin production, L-tryptophan is also a precursor to melatonin, a hormone that regulates sleep-wake cycles. Some people take L-tryptophan supplements to help improve sleep quality or manage mood disorders, but it's important to consult a healthcare professional before starting any supplementation.