Editing Tryptophan (section)

===Turkey meat and drowsiness hypothesis===
{{See also|Postprandial somnolence#Turkey and tryptophan}}

A common assertion in the US and the UK<ref>{{Cite news |last=Harding |first=Nick |date=2023-12-21 |title=How to stop Christmas food from ruining your sleep |language=en-GB |work=The Telegraph |url=https://www.telegraph.co.uk/health-fitness/wellbeing/sleep/why-christmas-foods-negatively-affect-sleep-quality/ |access-date=2023-12-25 |issn=0307-1235}}</ref> is that heavy consumption of [[turkey meat]]—as seen during [[Thanksgiving (United States)|Thanksgiving]] and [[Christmas]]—results in [[Somnolence|drowsiness]], due to high levels of tryptophan contained in turkey.<ref name = "McCue">{{cite web | vauthors = McCue K | title = Chemistry.org: Thanksgiving, Turkey, and Tryptophan | url = http://www.chemistry.org/portal/a/c/s/1/feature_ent.html?DOC=enthusiasts%5Cent_tryptophan.html | access-date = 2007-08-17 | archive-url = https://web.archive.org/web/20070404111342/http://www.chemistry.org/portal/a/c/s/1/feature_ent.html?DOC=enthusiasts%5cent_tryptophan.html | archive-date = 2007-04-04 }}</ref> However, the amount of tryptophan in turkey is comparable with that of other meats.<ref name = "scientificamerican" /><ref name = "USDA" /> [[Postprandial somnolence|Drowsiness after eating]] may be caused by other foods eaten with the turkey, particularly [[carbohydrate]]s.<ref name="HighBeam Research Interview">{{cite journal | title = Food & mood. (neuroscience professor Richard Wurtman) (Interview) | journal = Nutrition Action Healthletter | url = https://www.questia.com/read/1G1-12520128 |date=September 1992 }}{{dead link|date=July 2021}}</ref> Ingestion of a meal rich in carbohydrates triggers the release of [[insulin]].<ref name="pmid3279747">{{cite journal | vauthors = Lyons PM, Truswell AS | title = Serotonin precursor influenced by type of carbohydrate meal in healthy adults | journal = The American Journal of Clinical Nutrition | volume = 47 | issue = 3 | pages = 433–9 | date = March 1988 | pmid = 3279747 | doi =  10.1093/ajcn/47.3.433| doi-access = free }}</ref><ref name="pmid12499331">{{cite journal | vauthors = Wurtman RJ, Wurtman JJ, Regan MM, McDermott JM, Tsay RH, Breu JJ | title = Effects of normal meals rich in carbohydrates or proteins on plasma tryptophan and tyrosine ratios | journal = The American Journal of Clinical Nutrition | volume = 77 | issue = 1 | pages = 128–32 | date = January 2003 | pmid = 12499331 | doi =  10.1093/ajcn/77.1.128| doi-access = free }}</ref><ref name="pmid17284739">{{cite journal | vauthors = Afaghi A, O'Connor H, Chow CM | title = High-glycemic-index carbohydrate meals shorten sleep onset | journal = The American Journal of Clinical Nutrition | volume = 85 | issue = 2 | pages = 426–30 | date = February 2007 | pmid = 17284739 | doi =  10.1093/ajcn/85.2.426| doi-access = free }}</ref><ref name="Banks-2012">{{Cite journal|vauthors=Banks WA, Owen JB, Erickson MA|date=2012|title=Insulin in the Brain: There and Back Again|journal=Pharmacology & Therapeutics|volume=136|issue=1|pages=82–93|doi=10.1016/j.pharmthera.2012.07.006|issn=0163-7258|pmc=4134675|pmid=22820012}}</ref> Insulin in turn stimulates the uptake of large neutral [[branched-chain amino acids]] (BCAA), but not tryptophan, into muscle, increasing the ratio of tryptophan to BCAA in the blood stream. The resulting increased tryptophan ratio reduces competition at the [[large neutral amino acid transporter]] (which transports both BCAA and aromatic amino acids), resulting in more uptake of tryptophan across the [[blood–brain barrier]] into the [[cerebrospinal fluid]] (CSF).<ref name="Banks-2012" /><ref name="pmid1148286">{{cite journal | vauthors = Pardridge WM, [[William H. Oldendorf|Oldendorf WH]] | title = Kinetic analysis of blood-brain barrier transport of amino acids | journal = Biochimica et Biophysica Acta (BBA) - Biomembranes | volume = 401 | issue = 1 | pages = 128–36 | date = August 1975 | pmid = 1148286 | doi = 10.1016/0005-2736(75)90347-8 }}</ref><ref name="pmid6538743">{{cite journal | vauthors = Maher TJ, Glaeser BS, Wurtman RJ | title = Diurnal variations in plasma concentrations of basic and neutral amino acids and in red cell concentrations of aspartate and glutamate: effects of dietary protein intake | journal = The American Journal of Clinical Nutrition | volume = 39 | issue = 5 | pages = 722–9 | date = May 1984 | pmid = 6538743 | doi =  10.1093/ajcn/39.5.722}}</ref> Once in the CSF, tryptophan is converted into [[serotonin]] in the [[raphe nuclei]] by the normal enzymatic pathway.<ref name="pmid12499331" /><ref name="pmid5120086">{{cite journal|vauthors=Fernstrom JD, Wurtman RJ|date=1971|title=Brain serotonin content: increase following ingestion of carbohydrate diet|journal=Science|volume=174|issue=4013|pages=1023–5|doi=10.1126/science.174.4013.1023|pmid=5120086|bibcode=1971Sci...174.1023F|s2cid=14345137}}</ref> The resultant serotonin is further metabolised into the hormone [[melatonin]]—which is an important mediator of the [[circadian rhythm]]<ref>{{Cite journal |last=Atul Khullar |first=M. D. |date=2012-07-10 |title=The Role of Melatonin in the Circadian Rhythm Sleep-Wake Cycle |url=https://www.psychiatrictimes.com/view/role-melatonin-circadian-rhythm-sleep-wake-cycle |journal =Psychiatric Times | issue = 7 |language=en |volume=29}}</ref>—by the [[pineal gland]].<ref name="pmid4391290" /> Hence, these data suggest that "feast-induced drowsiness"—or [[postprandial somnolence]]—may be the result of a heavy meal rich in carbohydrates, which indirectly increases the production of melatonin in the brain, and thereby promotes sleep.<ref name="pmid3279747" /><ref name="pmid12499331" /><ref name="pmid17284739" /><ref name="pmid5120086" />