Used as a dietary supplement to support mental health, L-Tryptophan is known for its role in boosting serotonin production, which helps regulate mood, sleep, and appetite. It is commonly taken to alleviate symptoms of depression, anxiety, and insomnia. In the body, it converts into 5-HTP, a precursor to serotonin and melatonin, making it valuable for improving sleep quality and promoting relaxation. Some people use it to manage premenstrual syndrome (PMS) or to reduce carbohydrate cravings. It is also added to certain functional foods and beverages designed for stress relief and sleep support. In clinical settings, it has been studied for use in treating seasonal affective disorder (SAD) and other mood-related conditions.

In the pharmaceutical industry, it serves as a component in developing drugs related to the nervous system and is used in biochemical research on protein synthesis and brain function.

In animal nutrition, it is incorporated into animal feed to modulate behavior, such as reducing aggression in livestock, particularly pigs and poultry, to enhance growth efficiency and overall health.