tryptophan
Americannoun
noun
Etymology
Origin of tryptophan
1900–05; trypto- (irregular combining form representing Greek trīptós “rubbed”) + -phan(e) ( def. )
Explanation
Tryptophan is an amino acid that humans need in their diets in order to be healthy. Meat is known for providing lots of tryptophan. You may be familiar with tryptophan as the chemical present in turkey that is supposed to make people feel like taking a nap after their Thanksgiving feasts. In reality, scientists suspect that carbohydrates and alcohol — as well as overeating — are the true culprits in post-feast sleepiness. Tryptophan is important, though, since it helps our bodies synthesize the protein that we eat.
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Until now, however, researchers did not know what caused the brain to shift how it uses tryptophan in the first place.
From Science Daily • Jan. 15, 2026
Partly because I was exhausted from the tryptophan I had ingested with my turkey the day before and could not get out of bed.
From The Wall Street Journal • Nov. 28, 2025
No—they’re football tryptophan, a snoozy bore to watch.
From The Wall Street Journal • Nov. 24, 2025
Using a human intestinal cell line in the lab, they were able to isolate receptor DRD2 as the one that had the protective effect against infection in the presence of tryptophan metabolites.
From Science Daily • Mar. 13, 2024
Beans have both lysine and tryptophan, but not the amino acids cysteine and methionine, which are provided by maize.
From "1491" by Charles C. Mann
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
