November 11, 2022: Will the Tryptophan in Thanksgiving Turkey make you sleepy?


November 14, 2022

Will the Tryptophan in Thanksgiving Turkey make you sleepy?

Does eating Thanksgiving turkey make you sleepy due to its tryptophan content? Though the turkey myth has been debunked, as turkey contains no more tryptophan than any other common food or meat, there are other aspects of this myth that are worth exploring.

Tryptophan is an essential amino acid, meaning the body cannot produce it. It is ingested through the food we eat and is used to make various of our body’s proteins, including enzymes and neurotransmitters. One of its metabolic pathways includes the production of serotonin and melatonin. This hormone aids in maintaining our body’s natural circadian rhythm and is the source of the Thanksgiving turkey myth. A simplified metabolic pathway is illustrated below:


The pathway’s intermediate, 5-HTP (5-hydroxytryptophan), is not found in foods we naturally eat, but it may be derived from the plant seeds of Griffonia simplicifolia. 5-HTP is sold as a dietary supplement to aid sleep and mental health. However, in 1989 the FDA identified a dangerous contaminant, Peak X  in marketed 5-HTP supplements. While the FDA initially reported several cases of eosinophilic myalgia potentially linked to supplements contaminated with Peak X, causation was never confirmed. It remains unclear whether a potential contaminant such as Peak X caused the cases of eosinophilic myalgia.

However, the presence of Peak X and its potential toxicity caused the FDA to ban L-tryptophan and 5-HTP dietary supplements until the mid-2000s, today more Health Care Providers are concerned of possible drug interactions between L-tryptophan supplements and select antidepressants that may cause serotonin syndrome, a life-threatening condition. This is just one example of how dietary supplements may ultimately cause harm as well as wellness; therefore, patients, and healthcare providers need to have open conversations regarding their medication and supplement usage.


1. Maffei ME. 5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology. Int J Mol Sci. 2020;22(1):181.

2. Preuss H.G., Echard B., Talpur N., Funk K.A., Bagchi D. Does 5-hydroxytryptophan cause acute and chronic toxic perturbations in rats?Toxicol. Mech. Methods.  2006;16:281–286.

Question prepared by Juan Rodriguez, PharmD, PGY1 Pharmacy Resident, VUMC

Preceptor: Bob Lobo, PharmD, BCPS, FCCP: Director, Medication Use / Education / Research; Department of Pharmacy, VUMC

Comment: I bet that most of you believed the tryptophan myth. This is an interesting discussion highlighting some of the regulation issues regarding supplements. It can’t be said too often-supplements are not regulated by the FDA. There may be no consistency in amount of active ingredient in each pill. ds

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