Postprandial somnolence#Turkey and tryptophan

The exact cause of postprandial somnolence is unknown, but there are some scientific hypotheses:

Increases in glucose concentration excite and induce vasodilation in ventrolateral preoptic nucleus neurons of the hypothalamus via astrocytic release of adenosine that is blocked by A2A receptor antagonists like caffeine. Evidence also suggests that the small rise in blood glucose that occurs after a meal is sensed by glucose-inhibited neurons in the lateral hypothalamus.{{cite journal |last1=Burdakov |first1=Denis |last2=Jensen |first2=Lise Torp |last3=Alexopoulos |first3=Haris |last4=Williams |first4=Rhiannan Hope |last5=Fearon |first5=Ian M. |last6=O'Kelly |first6=Ita |last7=Gerasimenko |first7=Oleg |last8=Fugger |first8=Lars |last9=Verkhratsky |first9=Alexei |date=June 2006 |title=Tandem-pore K+ channels mediate inhibition of orexin neurons by glucose |journal=Neuron |volume=50 |issue=5 |pages=711–22 |doi=10.1016/j.neuron.2006.04.032 |pmid=16731510 |s2cid=15036932 |doi-access=free}} These orexin-expressing neurons appear to be hyperpolarised (inhibited) by a glucose-activated potassium channel. This inhibition is hypothesized to then reduce output from orexigenic neurons to aminergic, cholinergic, and glutamatergic arousal pathways of the brain, thus decreasing the activity of those pathways.{{cite journal | vauthors = Kosse C, Gonzalez A, Burdakov D | title = Predictive models of glucose control: roles for glucose-sensing neurones | journal = Acta Physiologica | volume = 213 | issue = 1 | pages = 7–18 | date = January 2015 | pmid = 25131833 | pmc = 5767106 | doi = 10.1111/apha.12360 }}

In response to the arrival of food in the stomach and small intestine, the activity of the parasympathetic nervous system increases and the activity of the sympathetic nervous system decreases.{{cite web|url=http://microvet.arizona.edu/Courses/VSC401/autonomicNervous.html|title=The Autonomic Nervous System|archive-url=https://web.archive.org/web/20080611073338/http://microvet.arizona.edu/Courses/VSC401/autonomicNervous.html|archive-date=11 June 2008|url-status=dead|access-date=12 June 2008}}{{cite web|url=http://www.ndrf.org/ans.html#The%20Parasympathetic%20System|title=The Parasympathetic Nervous System|last=Streeten|first=DVH|website=National Dysautonomia Research Foundation|access-date=18 July 2010}} This shift in the balance of autonomic tone towards the parasympathetic system results in a subjective state of low energy and a desire to be at rest, the opposite of the fight-or-flight state induced by high sympathetic tone. The larger the meal, the greater the shift in autonomic tone towards the parasympathetic system, regardless of the composition of the meal.{{Citation needed|date=November 2013}}

When foods with a high glycemic index are consumed, the carbohydrates in the food are more easily digested than low glycemic index foods. Hence, more glucose is available for absorption. It should not be misunderstood that glucose is absorbed more rapidly because, once formed, glucose is absorbed at the same rate. It is only available in higher amounts due to the ease of digestion of high glycemic index foods. In individuals with normal carbohydrate metabolism, insulin levels rise concordantly to drive glucose into the body's tissues and maintain blood glucose levels in the normal range.{{cite journal | vauthors = Jenkins DJ, Wolever TM, Taylor RH, Barker H, Fielden H, Baldwin JM, Bowling AC, Newman HC, Jenkins AL, Goff DV | title = Glycemic index of foods: a physiological basis for carbohydrate exchange | journal = The American Journal of Clinical Nutrition | volume = 34 | issue = 3 | pages = 362–6 | date = March 1981 | pmid = 6259925 | doi = 10.1093/ajcn/34.3.362 | doi-access = free }} Insulin stimulates the uptake of valine, leucine, and isoleucine into skeletal muscle, but not uptake of tryptophan. This lowers the ratio of these branched-chain amino acids in the bloodstream relative to tryptophan{{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 | url = http://www.ajcn.org/cgi/content/abstract/77/1/128 | doi-access = free }}{{cite journal | vauthors = Banks WA, Owen JB, Erickson MA | title = Insulin in the brain: there and back again | journal = Pharmacology & Therapeutics | volume = 136 | issue = 1 | pages = 82–93 | date = October 2012 | pmid = 22820012 | pmc = 4134675 | doi = 10.1016/j.pharmthera.2012.07.006 }} (an aromatic amino acid), making tryptophan preferentially available to the large neutral amino acid transporter at the blood–brain barrier.{{cite journal | vauthors = Boado RJ, Li JY, Nagaya M, Zhang C, Pardridge WM | title = Selective expression of the large neutral amino acid transporter at the blood-brain barrier | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 96 | issue = 21 | pages = 12079–84 | date = October 1999 | pmid = 10518579 | pmc = 18415 | doi=10.1073/pnas.96.21.12079| bibcode = 1999PNAS...9612079B | doi-access = free }} Uptake of tryptophan by the brain thus increases. In the brain, tryptophan is converted to serotonin,{{cite journal | vauthors = Fernstrom JD, Wurtman RJ | title = Brain serotonin content: increase following ingestion of carbohydrate diet | journal = Science | volume = 174 | issue = 4013 | pages = 1023–5 | date = December 1971 | pmid = 5120086 | doi = 10.1126/science.174.4013.1023 | bibcode = 1971Sci...174.1023F | s2cid = 14345137 }} which is then converted to melatonin. Increased brain serotonin and melatonin levels result in sleepiness.{{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 }}{{Cite web|url=http://www.montignac.com/en/the-glycemic-index-concept/|title=The Glycemic Index Concept {{!}} Official web site of the Montignac Method|website=www.montignac.com|language=en|access-date=17 March 2018}}

Insulin can also cause postprandial somnolence via another mechanism. Insulin increases the activity of Na/K ATPase, causing increased movement of potassium into cells from the extracellular fluid.{{cite web|url=http://www.vivo.colostate.edu/hbooks/molecules/sodium_pump.html|title=Sodium Pumps|date=29 April 2006|publisher=Vivo.colostate.edu|access-date=6 February 2013|archive-url=https://web.archive.org/web/20120729180756/http://www.vivo.colostate.edu/hbooks/molecules/sodium_pump.html|archive-date=29 July 2012|url-status=dead}} The large movement of potassium from the extracellular fluid can lead to a mild hypokalemic state. The effects of hypokalemia can include fatigue, muscle weakness, or paralysis.{{cite web|url=https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001510/|title=Hypokalemia - PubMed Health|publisher=Ncbi.nlm.nih.gov|access-date=6 February 2013}} The severity of the hypokalemic state can be evaluated using Fuller's Criteria.{{cite journal|url=https://online.epocrates.com/u/292159/Evaluation+of+hypokalemia/Diagnosis/Approach|title=Evaluation of hypokalemia Diagnostic Approach - Epocrates Online|journal=BMJ Case Reports|volume=2009|publisher=Online.epocrates.com|doi=10.1136/bcr.07.2008.0577|pmid=21686739|pmc=3027774|access-date=6 February 2013|year=2009|last1=Lin|first1=H. W.|last2=Chau|first2=T.|last3=Lin|first3=C. S.|last4=Lin|first4=S. H.}} Stage 1 is characterized by no symptoms but mild hypokalemia. Stage 2 is characterized with symptoms and mild hypokalemia. Stage 3 is characterized by only moderate to severe hypokalemia.

Cytokines are somnogenic and are likely key mediators of sleep responses to infection{{cite journal |last1=Krueger |first1=James M. |last2=Majde |first2=Jeannine A. |title=Microbial Products and Cytokines in Sleep and Fever Regulation |journal=Critical Reviews in Immunology |date=2017 |volume=37 |issue=2–6 |pages=291–315 |doi=10.1615/CritRevImmunol.v37.i2-6.70|pmid=29773024 }} and food.{{cite journal |last1=Lehrskov |first1=Louise L. |last2=Dorph |first2=Emma |last3=Widmer |first3=Andrea M. |last4=Hepprich |first4=Matthias |last5=Siegenthaler |first5=Judith |last6=Timper |first6=Katharina |last7=Donath |first7=Marc Y. |title=The role of IL-1 in postprandial fatigue |journal=Molecular Metabolism |date=June 2018 |volume=12 |pages=107–112 |doi=10.1016/j.molmet.2018.04.001|pmid=29705519 |doi-access=free |pmc=6001918 }} Some proinflammatory cytokines correlate with daytime sleepiness.{{cite journal |last1=van de Loo |first1=Aj |last2=Mackus |first2=M |last3=Knipping |first3=K |last4=Kraneveld |first4=Ad |last5=Garssen |first5=J |last6=Roth |first6=T |last7=Verster |first7=Jc |title=0785 Cytokines, Sleep, and Daytime Sleepiness |journal=Sleep |date=28 April 2017 |volume=40 |issue=suppl_1 |pages=A291 |doi=10.1093/sleepj/zsx050.784|doi-access=free }}

Although the passage of food into the gastrointestinal tract results in increased blood flow to the stomach and intestines, this is achieved by diversion of blood primarily from skeletal muscle tissue and by increasing the volume of blood pumped forward by the heart each minute.{{Citation needed|date=October 2019}} The flow of oxygen and blood to the brain is extremely tightly regulated by the circulatory system{{cite web|url=http://www.anaesthetist.com/physiol/basics/autoreg/Findex.htm#index.htm|title=Anesthetist: Vascular Autoregulation|website=Anaesthetist.com|access-date=12 June 2008}} and does not drop after a meal.

A common myth holds that turkey is especially high in tryptophan,{{cite web|url=http://chemistry.about.com/od/holidaysseasons/a/tiredturkey.htm|title=Does Eating Turkey Make You Sleepy?|last=Helmenstine|first=Anne Marie|publisher=About.com|access-date=13 November 2013|archive-date=7 August 2011|archive-url=https://web.archive.org/web/20110807044910/http://chemistry.about.com/od/holidaysseasons/a/tiredturkey.htm|url-status=dead}}{{cite web|url=http://home.howstuffworks.com/question519.htm|title=Is there something in turkey that makes you sleepy?|date=7 November 2007|publisher=HowStuffWorks|access-date=13 November 2013}}{{cite web|url=http://www.chemistry.org/portal/a/c/s/1/feature_ent.html?DOC=enthusiasts%5Cent_tryptophan.html|title=Thanksgiving, Turkey, and Tryptophan|last=McCue|first=Kevin|publisher=Chemistry.org|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=4 April 2007|url-status=|access-date=17 August 2007}} resulting in sleepiness after it is consumed, as may occur at the traditional meal of the North American holiday of Thanksgiving. However, the tryptophan content of turkey is comparable to chicken, beef, and other meats,{{cite web|url=http://www.ars.usda.gov/nutrientdata|title=USDA National Nutrient Database for Standard Reference, Release 20|last=Holden|first=Joanne|publisher=Nutrient Data Laboratory, Agricultural Research Service, United States Department of Agriculture|access-date=2 October 2007}} and does not result in higher blood tryptophan levels than other common foods. Certain foods, such as soybeans, sesame and sunflower seeds, and certain cheeses, are also high in tryptophan. Whether it is possible or not that these may induce sleepiness if consumed in sufficient quantities has yet to be studied.{{Medical citation needed|date=May 2021}}

A 2015 study, reported in the journal Ergonomics, showed that, for twenty healthy subjects, exposure to blue-enriched light during the post-lunch dip period significantly reduced the EEG alpha activity, and increased task performance.{{cite journal | vauthors = Baek H, Min BK | title = Blue light aids in coping with the post-lunch dip: an EEG study | journal = Ergonomics | volume = 58 | issue = 5 | pages = 803–10 | date = 2015 | pmid = 25559376 | doi = 10.1080/00140139.2014.983300 | s2cid = 5388522 }}

• Alkaline tide
• Food drunk
• Sugar high
• Glycemic index, a measure of how fast blood sugar levels rise
• Postprandial dip

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Category:Neurophysiology

Category:Metabolism

Category:Eating behaviors