After gorging yourself during tomorrow's Thanksgiving meal you may be strongly inclined to take a nap. Your family will likely blame the turkey's high tryptophan content as the trigger of your deep slumber, but I would suggest interrogating your mashed potatoes before convicting the gobbler.
While it is true that mega-doses of L-tryptophan (such as found in artificial supplements) may be useful as a sleep aid, the amount found in turkey (and other meats) is not enough to produce any meaningful change of your blood tryptophan levels or cause drowsiness. However, the mashed potatoes, stuffing and pies that accompany your beautifully bronzed-bird will likely help to exceed your typical meal's calorie and carbohydrate loads.. The sheer volume of food (calories) is partly to blame for sluggishness, but carbohydrate's physiologic effect is likely the main culprit. Carbohydrates (especially of high-glycemic index) produce a rush of insulin that effects the metabolism of tryptophan and subsequent serotinin produced your brain. Serotonin and it's byproduct melatonin in high levels can certainly cause drowsiness. In fact, they are the main chemical regulators of your sleep-wake cycle. (Interestingly, tryptophan is the precursor to serotonin which is probably how this whole myth got started in the first place!)
The turkey-tryptophan myth was "busted" on a recent episode of Mythbusters - albeit in a more humorous than scientific way. Also, the basics of tryptophan physiology (and the turkey myth) are reviewed in an excellent video by Scientific American.
Have a happy Thanksgiving and proceed with your annual rituals (including a post-meal recovery nap if you must), but don't blame the tryptophan!
W. Ryan Neuhofel, DO, MPH (Dr. Neu) is the physician and owner of NeuCare Family Medicine. He is a board-certified Family Physician (American Board of Family Medicine) and Fellow-candidate in Wilderness Medicine.
Information contained here is intended for general health education only. All personal health and medical issues should be managed by a health professional.
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