Way back on December 17, 2001, Craig Cowden asked, in a question concerning insomnia:
"Also, my students broadly know that certain foods, such as warm milk and turkey, contain a chemical (tyramine?) that is a precursor chemical to serotonin". In my reply on the same day, I suggested that the chemical in question was not tyramine but l-tryptophan, a precursor to serotonin with alleged sleep-inducing properties. I subsequently discovered that no less an authority than James Kalat, in the seventh edition of his _Biological Psychology_ (2001, p. 354) asserted, without reference, that "milk and turkey have relatively high amounts" of tryptophan. I thought no more than usual about this until the other day, when I was lecturing on serotonin and sleep, and a student again brought up turkey (the concept, not the upchuck) and l-tryptophan. In checking, I see that the _National Eosinophilia-Myalgia Syndrome Network_ (at http://www.nemsn.org/what%20caused%20EMS.htm) state "In its natural form LT ([l-tryptophan] is an amino acid found in foods as milk and turkey". Canada's own CBC Radio (at http://www.cbc.ca/news/radionews/context/biotech.html) says almost exactly the same thing. Do you see a trend here? What is it with turkey and l-tryptophan? Curiously, if you go back to reports in the 1970's (e.g. Kelly, 1972; "Talking turkey", 1971], turkey was under consideration as a treatment for psoriasis, only it was considered beneficial because it was claimed to be a _low_ tryptophan diet. Subsequently, it seems that someone noticed that people tend to get sleepy after stuffing themselves at Thanksgiving. Since the main event on that occasion is turkey, the "turkey coma" became conventional wisdom. Presumably someone then remembered those over-enthusiastic claims for l-tryptophan as a sleep-inducer, and decided to pin the blame for "turkey coma" on it. The explanation was that turkey is high in l-tryptophan, so when we get high on turkey, we fall asleep. As far as I can tell, this was the likely reason people switched from claiming that turkey was a low-tryptophan diet to claiming it was a high-tryptophan diet. A handy discussion of some of this, with debunking, is available on the web (Collard, 1999). So what's the straight dope on turkey? According to Collard (1999), who cites sources, turkey is unexceptional in the tryptophan department, having amounts comparable to that found in chicken or hamburger. Yet, as she points out, we don't talk about having a "chicken coma" or a "beef coma". A source I examined directly (Fisher & Scogall, 1982) provides confirmation. Turkey has about the same amount of tryptophan as in chicken, and if I'm interpreting the table correctly, the amount is actually quite low in comparison with other amino acids. So the next time a student asks about turkey and l-tryptophan, tell 'em it just ain't so. -Stephen References Talking Turkey (1971). The Lancet, December 25, 1410-1411 Kelly, A. (1972). Turkey diet regime in the treatment of psoriasis. British Journal of Dermatology, 86, 440-441 Collard, C. (1999). Turkey gets a bad rap: is it really a "turkey coma"? Website of the University of Florida College of Pharmacy, Virtual Drug Information Center http://www.cop.ufl.edu/vdis/ Fisher, C., & Scougall, R. (1982). A note on the amino acid composition of the turkey. British Poultry Science, 23, 233-37. ------------------------------------------------------------------------ Stephen Black, Ph.D. tel: (819) 822-9600 ext 2470 Department of Psychology fax: (819) 822-9661 Bishop's University e-mail: [EMAIL PROTECTED] Lennoxville, QC J1M 1Z7 Canada Department web page at http://www.ubishops.ca/ccc/div/soc/psy Check out TIPS listserv for teachers of psychology at: http://www.frostburg.edu/dept/psyc/southerly/tips/ ------------------------------------------------------------------------ --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
