Results implicating direct effects of tryptophan and serotonin on objective hot flashes will help guide the development of improved interventions for alleviating hot flashes in women with breast cancer. These interventions may target the central serotonin system either behaviorally (e.g., diet) or pharmacologically (e.g., alternative drug therapeutics). If direct manipulation of tryptophan and serotonin does not affect hot flashes, these findings will be equally as useful in guiding future research on non-serotonin related etiologies and interventions. Findings from this study will ultimately be used to eradicate hot flashes as a frequent, severe and bothersome breast cancer treatment related condition, thereby, improving quality of life for all women with breast cancer.