There is a myth that says the post-Thanksgiving dinner drowsiness is due to high amounts of tryptophan found in the turkey meat. Nothing farther from the truth; in fact, it is due to the high amounts of carbohydrates in the Thanksgiving dinner which trigger massive insulin production. Anyway, the myth still goes on, despite evidence that the turkey has about the same amount of tryptophan as the chicken. That being said, what’s this tryptophan business?
Tryptophan is an amino acid necessary for many things in the body, including the production of serotonin, a brain neurotransmitter. You cannot live without it and your body cannot make it. Thus, you need to eat it. There are many sources of tryptophan, like eggs, soybeans, cheeses, various meats and so on.
Tryptophan was first isolated by Hopkins & Cole (1901) through hydrolysis of casein, a protein found in milk. And there were no two ways about it: “there is indeed not the smallest doubt that our substance is the much-sought tryptophane” (p. 427). No “we’re confident that…”, “we’re suggesting this…”, no maybe, possibly, probably, and most likely’s that one finds in an overwhelming abundance in the cautious tone adopted by today’s studies. Many more scientists today, fewer job openings, one has a career to think about…
Digression aside, Hopkins went on later to prove that tryptophan is an essential amino acid by feeding mice a tryptophan-free diet (and the mice died). By 1929 he was knighted and he got the Nobel prize for his contributions in the vitamin field. Also, a little known fact for you, butter lovers, Hopkins proved that margarine is worse that butter because it lacks certain vitamins and you have him to thank for the vitamin-enriched margarine that you find today.
Reference: Hopkins FG & Cole SW (Dec 1901). A contribution to the chemistry of proteids: Part I. A preliminary study of a hitherto undescribed product of tryptic digestion. The Journal of Physiology, 27 (4-5): 418–28. doi:10.1113/jphysiol.1901.sp000880. PMC 1540554. PMID 16992614. Article | FREE FULLTEXT PDF
By Neuronicus, 27 November 2015